JP4345952B2 - High sensitivity light receiving element and image sensor - Google Patents

Description

(ただし、R₁₁は水素原子又は置換基を表し、該置換基の例としてはハロゲン原子、炭素原子数１〜12の置換又は無置換のアルキル基、炭素原子数７〜12の置換又は無置換のアラルキル基、炭素原子数６〜12の置換又は無置換のアリール基、前述の酸性基(これらの酸性基は塩を形成していてもよい)及びキレート化基が挙げられ、アルキル基及びアラルキル基のアルキル部分は直鎖状でも分岐状でもよく、またアリール基及びアラルキル基のアリール部分は単環でも多環(縮合環、環集合)でもよい。)により表される化合物から選ばれた有機配位子を表す。B-a、B-b及びB-cは同一でも異なっていてもよく、いずれか１つ又は２つでもよい。
【００３９】
有機金属錯体色素の好ましい具体例を以下に示すが、本発明はこれらに限定されるものではない。
【００４０】
【化２】

【００４１】
【化３】

【００４２】
(b)メチン色素
本発明に使用する色素の好ましいメチン色素は、シアニン色素、メロシアニン色素、スクワリリウム色素等のポリメチン色素である。本発明で好ましく用いられるポリメチン色素の例としては、特開平11-35836号、特開平11-67285号、特開平11-86916号、特開平11-97725号、特開平11-158395号、特開平11-163378号、特開平11-214730号、特開平11-214731号、特開平11-238905号、特開2000-26487号、欧州特許892411号、同911841号及び同991092号の各明細書に記載の色素が挙げられる。好ましいメチン色素の具体例を下に示すが、本発明はこれらに限定されるものではない。
【００４３】
【化４】

【００４４】
【化５】

【００４５】
(4)半導体微粒子への色素の吸着
半導体微粒子膜への色素の吸着は、色素の溶液中によく乾燥した半導体微粒子層を有する導電性支持体を浸漬するか、色素の溶液を半導体微粒子層に塗布する方法を用いることができる。前者の場合、浸漬法、ディップ法、ローラ法、エアーナイフ法等が使用可能である。浸漬法の場合、色素の吸着は室温で行ってもよいし、特開平7-249790号に記載されているように加熱還流して行ってもよい。また後者の塗布方法としては、ワイヤーバー法、スライドホッパー法、エクストルージョン法、カーテン法、スピン法、スプレー法等がある。色素を溶解する溶媒として好ましくは、アルコール類(メタノール、エタノール、t-ブタノール、ベンジルアルコール等)、ニトリル類(アセトニトリル、プロピオニトリル、3-メトキシプロピオニトリル等)、ニトロメタン、ハロゲン化炭化水素(ジクロロメタン、ジクロロエタン、クロロホルム、クロロベンゼン等)、エーテル類(ジエチルエーテル、テトラヒドロフラン等)、ジメチルスルホキシド、アミド類(N,N-ジメチルホルムアミド、N,N-ジメチルアセタミド等)、N-メチルピロリドン、1,3-ジメチルイミダゾリジノン、3-メチルオキサゾリジノン、エステル類(酢酸エチル、酢酸ブチル等)、炭酸エステル類(炭酸ジエチル、炭酸エチレン、炭酸プロピレン等)、ケトン類(アセトン、2-ブタノン、シクロヘキサノン等)、炭化水素(へキサン、石油エーテル、ベンゼン、トルエン等)及びこれらの混合溶媒が挙げられる。
【００４６】
色素の全吸着量は、多孔質半導体電極基板の単位表面積(１m²)当たり0.01〜100mmolとするのが好ましい。また色素の半導体微粒子に対する吸着量は、半導体微粒子１g当たり0.01〜１mmolの範囲であるのが好ましい。このような色素の吸着量とすることにより半導体における増感効果が十分に得られる。これに対し、色素が少なすぎると増感効果が不十分となり、また色素が多すぎると半導体に付着していない色素が浮遊し、増感効果を低減させる原因となる。色素の吸着量を増大させるためには、吸着前に加熱処理を行うのが好ましい。加熱処理後、半導体微粒子表面に水が吸着するのを避けるため、常温に戻さずに、半導体電極基板の温度が60〜150℃の間で素早く色素の吸着操作を行うのが好ましい。また、色素間の凝集などの相互作用を低減する目的で、無色の化合物を色素に添加し、半導体微粒子に共吸着させてもよい。この目的で有効な化合物は界面活性な性質、構造をもった化合物であり、例えばカルボキシル基を有するステロイド化合物(例えばケノデオキシコール酸)又は下記の例のようなスルホン酸塩類が挙げられる。
【００４７】
【化６】

【００４８】
未吸着の色素は、吸着後速やかに洗浄により除去するのが好ましい。洗浄は湿式洗浄槽を使い、アセトニトリル等の極性溶剤、アルコール系溶剤のような有機溶媒を用いるのが好ましい。色素を吸着した後にアミン類や４級塩を用いて半導体微粒子の表面を処理してもよい。該アミン類は好ましくはピリジン、4-t-ブチルピリジン、ポリビニルピリジン等であり、４級塩は好ましくはテトロブチルアンモニウムヨージド、テトラヘキシルアンモニウムヨージド等ある。これらが液体の場合はそのまま用いてもよいし、有機溶媒に溶解して用いてもよい。
【００４９】
（C）イオン伝導性電解質層
イオン伝導性電解質層に用いる電解質は、イオン伝導性材料であれば特に限定されるものではなく、従来公知の電解質であれば何れを用いてもよい。電解質中に含まれるイオンの種類は特に限定されないが、作動電圧（素子に使用する材料や構成により変化するが通常１V以下）において酸化も還元も受けず、電子伝導性の無い安定なものが好ましい。本発明で用いることのできる代表的な電解質の例としては、イオンが溶解した溶液（電解液）、電解液をポリマーマトリクスのゲルに含浸したいわゆるゲル電解質、溶融塩電解質、ポリマー電解質や無機固体電解質（伝導性のイオン結晶など）等の固体電解質が挙げられる。
【００５０】
(1)溶融塩電解質
溶融塩電解質とは、室温において液状であるか、又は低融点の塩であり、例えばWO95/18456号、特開平8-259543号、電気化学，第65巻，11号，923頁（1997年）等に記載されているピリジニウム塩、イミダゾリウム塩、トリアゾリウム塩等の既知の電解質を挙げることができる。溶融塩の融点は100℃以下であるのが好ましく、室温付近において液状となるが特に好ましい。
【００５１】
本発明では、下記一般式（Y-a）、（Y-b）及び（Y-c）：
【化７】

のいずれかにより表される溶融塩が好ましく使用できる。
【００５２】
一般式（Y-a）中、Q_y1は窒素原子と共に５又は６員環の芳香族カチオンを形成しうる原子団を表す。Q_y1は炭素原子、水素原子、窒素原子、酸素原子及び硫黄原子からなる群から選ばれる１種以上の原子により構成されるのが好ましい。Q_y1が形成する５員環は、オキサゾール環、チアゾール環、イミダゾール環、ピラゾール環、イソオキサゾール環、チアジアゾール環、オキサジアゾール環、トリアゾール環、インドール環又はピロール環であるのが好ましく、オキサゾール環、チアゾール環又はイミダゾール環であるのがより好ましく、オキサゾール環又はイミダゾール環であるのが特に好ましい。Q_y1が形成する６員環は、ピリジン環、ピリミジン環、ピリダジン環、ピラジン環又はトリアジン環であるのが好ましく、ピリジン環であるのが特に好ましい。
【００５３】
一般式（Y-b）中、A_y1は窒素原子又はリン原子を表す。
【００５４】
一般式（Y-a）、（Y-b）及び（Y-c）中のX^-はアニオンを表し、ハロゲン化物イオン（Cl^-、Br^-、I^-等）、SCN^-、BF₄ ^-、PF₆ ^-、ClO₄ ^-、(CF₃SO₂)₂N^-、(CF₃CF₂SO₂)₂N^-、CH₃SO₃ ^-、CF₃SO₃ ^-、CF₃COO^-、Ph₄B^-、(CF₃SO₂)₃C^-等が好ましい例として挙げられ、SCN^-、CF₃SO₃ ^-、CF₃COO^-、(CF₃SO₂)₂N^-又はBF₄ ^-であるのがより好ましい。
【００５５】
一般式（Y-a）、(Y-b)及び（Y-c）中のR_y1〜R_y11はそれぞれ独立に置換又は無置換のアルキル基（好ましくは炭素原子数１〜24であり、直鎖状であっても分岐状であっても、また環式であってもよく、例えばメチル基、エチル基、プロピル基、イソプロピル基、ペンチル基、ヘキシル基、オクチル基、2-エチルヘキシル基、t-オクチル基、デシル基、ドデシル基、テトラデシル基、2-ヘキシルデシル基、オクタデシル基、シクロヘキシル基、シクロペンチル基等）、或いは置換又は無置換のアルケニル基（好ましくは炭素原子数２〜24であり、直鎖状であっても分岐状であってもよく、例えばビニル基、アリル基等）を表す。より好ましくは炭素原子数２〜18のアルキル基又は炭素原子数２〜18のアルケニル基であり、特に好ましくは炭素原子数２〜６のアルキル基である。
【００５６】
また、一般式（Y-b）中のR_y2〜R_y5のうち２つ以上が互いに連結してA_y1を含む非芳香族環を形成してもよく、一般式（Y-c）中のR_y6〜R_y11のうち２つ以上が互いに連結して環構造を形成してもよい。
【００５７】
上記Q_y1及びR_y1〜R_y11は置換基を有していてもよい。好ましい置換基の例としては、ハロゲン原子（F、Cl、Br、I等）、シアノ基、アルコキシ基（メトキシ基、エトキシ基、メトキシエトキシ基、メトキシエトキシエトキシ基等）、アリーロキシ基（フェノキシ基等）、アルキルチオ基（メチルチオ基、エチルチオ基等）、アルコキシカルボニル基（エトキシカルボニル基等）、炭酸エステル基（エトキシカルボニルオキシ基等）、アシル基（アセチル基、プロピオニル基、ベンゾイル基等）、スルホニル基（メタンスルホニル基、ベンゼンスルホニル基等）、アシルオキシ基（アセトキシ基、ベンゾイルオキシ基等）、スルホニルオキシ基（メタンスルホニルオキシ基、トルエンスルホニルオキシ基等）、ホスホニル基（ジエチルホスホニル基等）、アミド基（アセチルアミノ基、ベンゾイルアミノ基等）、カルバモイル基（N,N-ジメチルカルバモイル基等）、アルキル基（メチル基、エチル基、プロピル基、イソプロピル基、シクロプロピル基、ブチル基、2-カルボキシエチル基、ベンジル基等）、アリール基（フェニル基、トルイル基等）、複素環基（ピリジル基、イミダゾリル基、フラニル基等）、アルケニル基（ビニル基、1-プロペニル基等）、シリル基、シリルオキシ基等が挙げられる。
【００５８】
一般式（Y-a）、（Y-b）又は（Y-c）により表される溶融塩は、Q_y1又はR_y1〜R_y11を介して多量体を形成してもよい。
【００５９】
これらの溶融塩は、単独で使用しても、２種以上混合して使用してもよい。また、LiIやCF₃COOLi、CF₃COONa、LiSCN、NaSCN等のアルカリ金属塩を添加することもできる。アルカリ金属塩の添加量は、0.02〜２質量％程度であるのが好ましく、0.1〜１質量％がさらに好ましい。
【００６０】
本発明で好ましく用いられる溶融塩の具体例を以下に挙げるが、これらに限定されるわけではない。
【００６１】
【化８】

【００６２】
【化９】

【００６３】
【化１０】

【００６４】
【化１１】

【００６５】
【化１２】

【００６６】
【化１３】

【００６７】
上記溶融塩電解質は常温で溶融状態であるのが好ましく、これを含有する組成物には溶媒を用いない方が好ましい。後述する溶媒を添加しても構わないが、溶融塩の含有量は電解質組成物全体に対して50質量％以上であるのが好ましく、90質量％以上であるのが特に好ましい。
【００６８】
(2)電解液
イオン伝導性電解質層に電解液を使用する場合、電解液は電解質塩、溶媒、及び添加物から構成されることが好ましい。
【００６９】
電解質塩は、溶媒に溶解し、電離するものであれば、特に限定されない。具体的には、前記(1) 溶融塩電解質で例示したような有機カチオンあるいは金属カチオン（Li⁺、K⁺、Na⁺、Ce²⁺など）と一般式（Y-a）、（Y-b）、（Y-c）のアニオンX^-を組み合わせた電解質塩が好ましい例として挙げられる。
【００７０】
電解質に使用する溶媒は、粘度が低くイオン移動度を向上したり、もしくは誘電率が高く有効キャリアー濃度を向上したりして、優れたイオン伝導性を発現できる化合物であることが望ましい。このような溶媒としては、エチレンカーボネート、プロピレンカーボネート等のカーボネート化合物、3-メチル-2-オキサゾリジノン等の複素環化合物、ジオキサン、ジエチルエーテル等のエーテル化合物、エチレングリコールジアルキルエーテル、プロピレングリコールジアルキルエーテル、ポリエチレングリコールジアルキルエーテル、ポリプロピレングリコールジアルキルエーテル等の鎖状エーテル類、メタノール、エタノール、エチレングリコールモノアルキルエーテル、プロピレングリコールモノアルキルエーテル、ポリエチレングリコールモノアルキルエーテル、ポリプロピレングリコールモノアルキルエーテル等のアルコール類、エチレングリコール、プロピレングリコール、ポリエチレングリコール、ポリプロピレングリコール、グリセリン等の多価アルコール類、アセトニトリル、グルタロジニトリル、メトキシアセトニトリル、プロピオニトリル、ベンゾニトリル等のニトリル化合物、ジメチルスルホキシド、スルホラン等の非プロトン極性物質、水等が挙げられ、これらを混合して用いることもできる。
【００７１】
(3)ゲル電解質
本発明では、電解質はポリマー添加、オイルゲル化剤添加、多官能モノマー類を含む重合、ポリマーの架橋反応等の手法により、前述の溶融塩電解質や電解液をゲル化（固体化）させて使用することもできる。ポリマー添加によりゲル化させる場合は、“Polymer Electrolyte Reviews-１及び２”(J.R.MacCallumとC.A. Vincentの共編、ELSEVIER APPLIED SCIENCE)に記載された化合物を使用することができるが、特にポリアクリロニトリル及びポリフッ化ビニリデンを好ましく使用することができる。オイルゲル化剤添加によりゲル化させる場合はJ. Chem Soc. Japan, Ind. Chem.Sec., 46,779(1943), J. Am. Chem. Soc., 111,5542(1989), J. Chem. Soc., Chem. Commun., 1993, 390, Angew. Chem. Int. Ed. Engl., 35,1949(1996), Chem. Lett., 1996, 885, J. Chm. Soc., Chem. Commun., 1997,545に記載されている化合物を使用することができるが、好ましい化合物は分子構造中にアミド構造を有する化合物である。電解液をゲル化した例は特開平11-185863号に、溶融塩電解質をゲル化した例は特開2000-58140号に記載されており、これらも本発明にも適用できる。
【００７２】
また、ポリマーの架橋反応により電解質をゲル化させる場合、架橋可能な反応性基を含有するポリマー及び架橋剤を併用することが望ましい。この場合、好ましい架橋可能な反応性基は、アミノ基、含窒素複素環（ピリジン環、イミダゾール環、チアゾール環、オキサゾール環、トリアゾール環、モルホリン環、ピペリジン環、ピペラジン環等）等であり、好ましい架橋剤は、窒素原子に対して求電子反応可能な２官能以上の試薬（ハロゲン化アルキル、ハロゲン化アラルキル、スルホン酸エステル、酸無水物、酸クロライド、イソシアネート、α、β-不飽和スルホニル基、α、β-不飽和カルボニル基、α、β-不飽和ニトリル基等）であり、特開2000-17076号、同2000-86724号に記載されている架橋技術も適用できる。
【００７３】
(4)高分子固体電解質
高分子化合物としては、高分子化合物自体が電解質塩を溶解してイオン伝導性を示すもの、或いは、高分子化合物自体は電解質を溶解できないものであっても電解質を溶解することができる溶媒を用いて、高分子化合物がイオン伝導性を示すようになるものを用いることができる。
【００７４】
前者の高分子化合物の例としては、ポリエチレングリコール、主鎖にポリアクリル酸、ポリメタクリル酸、ポリエチレンオキシド、ポリプロピレンオキシド、ポリビニルアルコール、ポリフォスファゼン、ポリシラン等、及びそれらの共重合体等で、側鎖にポリオキシエチレン構造を有する高分子化合物等を用いることができる。これらの電解質を溶解できる高分子化合物であっても、前述の電解質塩を溶解することができる溶媒を併用することができる。
【００７５】
これに対して、後者の高分子化合物の例としては、ポリ塩化ビニル、ポリアクリロニトリル、ポリエチレン、ポリプロピレン、ポリエステル、ポリアクリレート及びそれらの共重合体等を用いることができる。なお、上述の高分子化合物は、架橋構造を有するものであっても良い。
【００７６】
(5)電解質中の添加物
また、本発明では、J. Am. Ceram. Soc.,80 (12)3157-3171(1997)に記載されているようなtert-ブチルピリジン、2-ピコリン、2,6-ルチジン等の塩基性化合物を前述の溶融塩電解質又は電解液に添加することが好ましい。塩基性化合物を添加する場合の好ましい濃度範囲は0.05M〜２Mである。
【００７７】
(6)イオン伝導性電解質層の形成
イオン伝導性電解質層の形成方法に関しては２通りの方法が考えられる。１つは感光層の上に先に対極を貼り合わせておき、その間隙に液状の電解質を挟み込む方法である。もう１つは感光層上に直接、電解質を付与する方法で、対極はその後付与することになる。
【００７８】
前者の方法の場合、電解質の挟み込み方法として、浸漬等による毛管現象を利用する常圧プロセス、又は常圧より低い圧力にして間隙の気相を液相に置換する真空プロセスを利用できる。
【００７９】
後者の方法の場合、湿式のイオン伝導性電解質層においては未乾燥のまま対極を付与し、エッジ部の液漏洩防止措置を施すことになる。またゲル電解質の場合には湿式で塗布して重合等の方法により固体化する方法があり、その場合には乾燥、固定化した後に対極を付与することもできる。
【００８０】
固体電解質の場合には真空蒸着法やCVD法等のドライ成膜処理でイオン伝導性電解質層を形成し、その後対極を付与することもできる。
【００８１】
（D）下塗り層
対極と導電性支持体の短絡を防止するため、導電性支持体と感光層の間には、緻密な半導体の薄膜層を下塗り層として予め塗設しておくことが好ましい。この下塗り層による短絡を防止する方法は、イオン伝導性電解質層に電子輸送材料や正孔輸送材料を用いる場合は特に有効である。下塗り層は好ましくはTiO₂、SnO₂、Fe₂O₃、WO₃、ZnO又はNb₂O₅からなり、さらに好ましくはTiO₂からなる。下塗り層は、例えばElectrochim. Acta 40, 643-652(1995)に記載されているスプレーパイロリシス法の他、スパッタ法等により塗設することができる。下塗り層の好ましい膜厚は5〜1000nmであり、10〜500nmがさらに好ましい。
【００８２】
（E）受光素子の内部構造の具体例
上述のように、受光素子の内部構造は目的に合わせ様々な形態が可能である。大きく２つに分ければ、両面から光の入射が可能な構造と、片面からのみ可能な構造が可能である。図２〜図６に本発明に好ましく適用できる受光素子の内部構造を例示する。
【００８３】
図２は、透明導電層10aと10a'との間に、感光層20と20'及びイオン伝導性電解質層30とを介在させたものであり、両面から光が入射する構造となっている。図３は、透明基板40a上に一部金属リード11を設け、さらに透明導電層10aを設け、下塗り層50、感光層20、イオン伝導性電解質層30、感光層20'、下塗り層50'、及び導電層10'をこの順で設け、さらに支持基板40'を配置したものであり、透明基板40a側から光が入射する構造となっている。図４は、図３の基板40'と導電層10'を透明基板40a'と透明導電層10a'に換え、さらに、透明基板40a'上、透明導電層10a'内に、一部金属リード11を設けたものであり、両面から光が入射する構造である。図５は、図４の下塗り層50,50'と金属リードを取り除いたものであり、同じく両面から光が入射する構造である。図６は、図５の透明基板40a'と透明導電層10a'を基板40'と導電層10'に換えたものであり、基板40a側から光が入射する構造である。
【００８４】
[2] 積層型カラーセンサー
本発明の受光素子をカラーセンサーとして応用した例について述べる。これは、[1]で述べた本発明の受光素子の構成を複数、又は、本発明の受光素子の構成に本発明の受光素子構成の一方の感光層を対極とした素子構成を組み合わせて、光の入射方向に積層した新規な層構成を有するものである。この場合、各感光層の感光波長領域が異なることが好ましい。
【００８５】
本発明の受光素子を用いたカラー光センサーは、感光波長領域の異なる複数の半導体電極と、イオン伝導性電解質層とを有し、また、場合によっては対極を有し、上記感光波長領域の異なる複数の半導体電極又は対極は相互に間隙を設けて積層され、各半導体電極間又は対極との間隙にはイオン伝導性電解質層が充填されている。それぞれの層の境界では、各層の構成成分同士が相互に拡散混合していてもよい。
【００８６】
ここで用いる半導体電極及びイオン伝導性電解質層は、前述[1]で述べたものと同様のものを用いることができる。
【００８７】
ここで用いる対極は上記の導電性支持体と同様に、導電性材料からなる対極導電層の単層構造でもよいし、対極導電層と支持基板から構成されていてもよい。対極導電層に用いる導電材としては、金属(白金、金、銀、銅、アルミニウム、マグネシウム、インジウム等)、炭素、又は導電性金属酸化物(インジウム−スズ複合酸化物、フッ素ドープ酸化スズ等)が挙げられる。この中でも白金、金、銀、銅、アルミニウム又はマグネシウムを対極層として好ましく使用することができる。対極の好ましい支持基板の例は、ガラス又はプラスチックであり、これに上記の導電剤を塗布又は蒸着して用いる。対極導電層の厚さは特に制限されないが、３〜10 nmが好ましい。対極層の表面抵抗は低い程よい。好ましい表面抵抗の範囲としては50Ω／□以下であり、さらに好ましくは20Ω／□以下である。
【００８８】
対極は、イオン伝導性電解質層上に直接導電材を塗布、メッキ又は蒸着(PVD、CVD)するか、導電層を有する基板の導電層側を貼り付ければよい。また、導電性支持体の場合と同様に、特に対極が透明の場合には、対極の抵抗を下げる目的で金属リードを用いるのが好ましい。なお、好ましい金属リードの材質及び設置方法、金属リード設置による入射光量の低下等は導電性支持体の場合と同じである。
【００８９】
また、設置される環境に応じて、電極として作用する導電性支持体と対極の一方又は両方の外側表面、導電層と基板の間又は基板の中間に、保護層、反射防止層等の機能性層を設けても良い。これらの機能性層の形成には、その材質に応じて塗布法、蒸着法、貼り付け法等を用いることができる。
対極は、感光波長領域の異なる半導体電極に対応して複数設けても良いし、複数の半導体電極に共通する共通対極を１層のみ設けてもよい。後者の場合、上記複数の半導体電極のすべてがイオン伝導性電解質層を介して対極と電気的に接触している必要があるため、半導体電極及び／又は対極に電荷移動用のリーク孔を設ける。
【００９０】
上記のカラー光センサーの構成に加えて、機械的強度を付与するため、必要に応じて導電層及び／又は対極に支持体を設けてもよい。支持体の片面にのみ半導体電極（対極）を設けても良いし、支持体の両面にそれぞれ感光波長領域の異なる２層の半導体電極（対極）を設けても良い。
【００９１】
本発明においては、感光波長領域の異なる複数の半導体電極のすべての感光層に光を到達させる必要があるため、前述の光入射側の半導体感光層（たとえば青色感光層）を担持した導電層（及び必要に応じて用いるその支持体）が実質的に光学的に透明でなければならない。また、その他の色素増感半導体感光層を担持する導電層や支持体も同様に透明であり、上層の感光層を透過した光が導電層を透過し下層の感光層に至る状況が満足されていなければならない。ただし、最下層の感光層の導電層及びその支持体は、その下層に感光層が配置していない場合は、不透明であってもよい。同様に、最下層が対極である場合は、対極及びその支持体は不透明であってよい。
【００９２】
カラー光センサーの分光性を向上するためには、各半導体電極がシャープな分光波長特性を有することが好ましく、半導体電極のうち少なくとも１層は、色素を吸着した半導体微粒子を感光層に含有することが好ましい。具体的には、青色（B）、緑色（G）、赤色（R）の３色の波長領域にそれぞれ独立に強い吸収を持った色素増感半導体電極を設けることが好ましい。なお、色素を吸着しない半導体電極とする場合、半導体層には可視光波長領域に光学吸収を持つ半導体が用いられ、このような半導体としては、例えばCdS，CdSe，GaAs、GaP，Si等の半導体が有効である。
【００９３】
また、感光波長領域の異なる半導体感光層が積層された構造において、光入射側に最も近い感光層から最も遠い感光層向かって、感光波長が長波長となる順序で配置することが好ましい。また、半導体感光層が青色感光層（B層）、緑色感光層（G層）、赤色感光層（R層）の３層からなる場合、光入射側から順次、B層、G層、R層の順で配置されていることが好ましい。この場合、B層と対極及びG層とR層がそれぞれイオン伝導性電解質を介する構成であっても、B層とG層及びR層と対極がそれぞれイオン伝導性電解質を介する構成であってもよい。
【００９４】
本発明の受光素子の内部構造は、たとえば、図７〜図９に示すように目的に合わせ様々な形態が可能である。
【００９５】
図７は本発明に基づいたもっとも単純な構成の例であり、３層の半導体電極と、１層の対極を用いた構成の例である。第１の透明基板40aの下面に透明な青色感光層20Bを設け、第２の透明基板40a'上面に透明な緑色感光層20Gを設けるとともに下面に赤色感光層20Rを設け、第３の基板40の上面に対極60を設け、上記青色感光層20Bと緑色感光層20Gとの間及び、赤色感光層20Rと対極60との間にそれぞれイオン伝導性電解質層30と30’を充填した構成からなる。ここで光は、青色感光層20B側から入射して、青色感光層20Bを一部透過して緑色感光層20Gへ、次いで赤色感光層20Rへと到達する。
【００９６】
図８は、図７の対極を中間に配した例であり、第１の透明基板40aの下面に透明な青色感光層20Bを設け、第２の透明基板40a'の上面に透明対極60aを設けるとともに下面に透明な緑色感光層20Gを設け、第３の基板40上に赤色感光層20Rを設け、上記青色感光層20Bと透明対極60aとの間、緑色感光層20Gと赤色感光層20Rとの間にそれぞれイオン伝導性電解質層30と30’を充填した構成からなる。
【００９７】
また、図９のように、透明基板40aから40a'までの素子と40a''と40a'''までの素子を組み立て、透明基板40a'と40a''を接着して積層型素子とすることもできる。
【００９８】
尚、本発明の受光素子を用いた光電変換型カラー光センサーの内部構造は、図７と図８に限定されるものではなく、例えば積層順序を入れ替えたり、２層あるいは４層以上の半導体電極を用いた構成にすることもできる。
【００９９】
上記のような構成のカラー光センサーは、感光波長領域の異なる半導体電極において、各感光波長領域の光の強度に応じた光電流が電解質を挟んで対向する電極間で生じる。これを外部回路によって検知することにより、入射光の色（波長）とその強度をセンシングすることができる。
【０１００】
感光波長域の異なる半導体電極を素子に用いることにより、それぞれ異なる波長の光に対して上記の光電流を観測できるので、カラー光センサーとして機能することができる。
【０１０１】
異なる感光波長領域を有する複数の半導体電極を積層させた上記のカラー光センサーをひとつの画素として、これを二次元的に複数個配列させることにより、カラーのイメージセンサーを形成することができる。これにより、二次元の画像情報を電気信号として得ることができる。
【０１０２】
イメージセンサーは、これを構成する画素、すなわち単位となるカラー光センサーを小さくし、その数を多くすることにより、画像の空間分解能を向上させることができ、大面積化を実現できる。イメージセンサーの構成においては、全ての画素の対極をひとつの共通対極とすることもできる。
【０１０３】
【実施例】
以下、本発明を実施例によって具体的に説明するが、本発明はこれらに限定されるものではない。
【０１０４】
実施例１．微分応答型受光素子
1-1 二酸化チタン分散液の調製
内側をテフロンコーティングした内容積200mlのステンレス製ベッセルに二酸化チタン（日本アエロジル社 Degussa P-25）15g、水45g、分散剤（アルドリッチ社製、Triton Ｘ-100）１g、直径0.5mmのジルコニアビーズ（ニッカトー社製）30gを入れ、サンドグラインダーミル（アイメックス社製）を用いて1500rpmにて２時間分散した。分散物からジルコニアビーズをろ過して除いた。この場合の二酸化チタンの平均粒径は25nmであった。このときの粒径はMALVERN社製マスターサイザーにて測定したものである。
【０１０５】
1-2 色素を吸着したTiO₂電極（電極A）の作成
フッ素をドープした酸化スズをコーティングした導電性ガラス（旭硝子製TCOガラスを20mm×100mmの大きさに切断加工したもの）の導電面側にガラス棒を用いて上記の分散液を塗布した。この際導電面側の一部（端から３mm）に粘着テープを張ってスペーサーとし、粘着テープが両端に来るように塗布した。塗布後、粘着テープを剥離し、室温で１日間風乾した。次に、このガラスを20mm×15mmに裁断し、図10(a)のようにTiO₂面を削り、導電面を露出させた。このガラスを電気炉（ヤマト科学製マッフル炉FP-32型）に入れ、450℃にて30分間焼成した。このガラスを取り出し冷却した後、青色吸収色素(DB-1)のエタノール（19ml）/ジメチルスルホキシド(1ml)溶液（３×10^-4mol/L）に３時間浸漬し、エタノールで洗浄し自然乾燥させ、色素吸着TiO₂層400を有する青色感光性半導体(BE-1)を作成した。緑色吸収色素(DG-1)、赤色吸収色素(DR-1)を用いる他は同様にして、緑色感光性半導体(GE-1)、赤色感光性半導体(RE-1)を作成した。またDB-1、DG-1及びDR-1の各色素の構造を以下に示す。
【０１０６】
【化１４】

【０１０７】
1-3 受光素子の作成
上述のようにして作成したTiO₂電極基板BG-1の導電性面に、図10(b)に示すように、スペーサー500として熱収縮性樹脂シート（デュポン社製、商品名FUSABONDO）を熱融着した。次に、スペーサーを熱融着したGE-1と上記で作成したBE-1を図10(c)に示すようにTiO₂面が重なって対向するように重ね合わせ、圧力をかけながら熱融着した。この青色感光性半導体(BE-1)600と緑色感光性半導体(GE-1)700の間隙に、スペーサー500に設けた４隅の注入口510から表１に示した電解質E-101を注入した。注入後、４隅の注入口をエポキシ樹脂で塞ぎ、本発明の受光素子BG-101を作成した。表１に示した、色素増感半導体電極の感光性半導体と電解質を換えた他の素子BG-102〜104、GR-101〜104も同様の方法で作成した。
【０１０８】
【表１】

【０１０９】
1-4．受光素子の光-電流応答測定
上述のようにして作成した受光素子（BG-101）の青色感光性半導体（BE-1）側と光源のランプ（92mW）との間に、B,G,Rのカラーフィルターと、図11に示した回転円盤スリットを配置した。受光素子のBE-1導電面にポテンショスタットの作用極端子を、受光素子のGE-1導電面にポテンショスタットの対極端子と参照極端子を接続し、ポテンショスタットの電位を０Vに設定した。円盤スリットを300rpmの速さで回転させながら、カラーフィルターを通して、B光、G光及びR光を青色感光性半導体（BE-1）側に照射し、電流値を検出した。
【０１１０】
図12に、B光、G光及びR光を照射した時の電流応答を示した。B光を照射した場合には、図12に示すように、受光面に光が照射された瞬間にプラス電流応答、光がスリットに遮られた瞬間にマイナス電流応答が得られ、G光が照射された場合には、B光照射時と逆の電流応答が得られた。またR光照射時には、わずかな電流応答しか得られなかった。
【０１１１】
表２に、受光素子面に、スリットから光が照射された瞬間に流れる電流のピーク値を示した。
【０１１２】
【表２】

【０１１３】
以上の結果から、本発明の受光素子は、２色の光に感応する高感度な受光素子であることが明らかとなった。
【０１１４】
実施例２ .積層型受光素子
2-1 積層型受光素子の作成
1-1で使用したものと同じ導電性ガラスを15mm×20mmに切断し、図13(a)に示すように、スペーサー500として、熱収縮性樹脂シート（デュポン社製、商品名FUSABONDO）を熱融着した。この導電性ガラス（透明対極）900と1-2で作成した青色感光性半導体(BE-1)600を、図13(b)に示すように重ね合わせ、圧力をかけながら熱融着した。スペーサー500に設けた注入口510より、電解液E-101を注入し、エポキシ樹脂で注入口を塞ぎ、青色感光素子B-101を作成した。次に、B-101と1-3で作成した素子GR-101を図13(c)に示すように、B-101の対極側のガラス面とGR-101のGE-1側のガラス面を重ね合わせ、重ね合わせたガラスの淵をエポキシ樹脂で接着した。これにより青色感光性半導体(BE-1)600、透明対極900、緑色感光性半導体(GE-1)700及び赤色感光性半導体(RE-1)800を積層した積層型カラーセンサーBGR-101を作成した。
【０１１５】
2-2 積層型カラーセンサーの光電流応答の測定
上記で作成した積層型カラーセンサーBGR-1を用い、1-4と同様の方法にて、B,G,R光をBE-1面から照射した時のBE-1と対極の電流応答とGE-1とRE-1の間の電流応答を、２台のポテンショスタットを使用し、独立に検出した。
【０１１６】
2-3 積層型受光素子の光-電流応答測定
図14〜16に、円盤スリットを抜けて、光が受光面に照射された瞬間から、スリットが閉じるまでの、BE-1／対極間及びGE-1／RE-1間の電流応答を示す。B光を照射した場合、BE-1／対極間に大きなプラスの電流応答が得られ、G光照射時は、GE-1とRE-1間にプラスの電流応答が、R光照射時には、GE-1とRE-1間にマイナスの電流応答が得られた。以上のように、本積層型受光素子では、極めて簡単な構成により、BGR光変化が微分電流応答として検出できることがわかった。
【０１１７】
【発明の効果】
以上詳述したように、本発明の受光素子は感度及び分光波長特性に優れ、光画像の動的変化や輪郭抽出を容易に行うことを可能にした。また感光層の重層構成によってより多くの色情報及び光の動的情報を同時に検出することを可能にした。
【図面の簡単な説明】
【図１】 本発明の好ましい受光素子の構造を示す部分断面図である。
【図２】 本発明の好ましい受光素子の構造を示す部分断面図である。
【図３】 本発明の好ましい受光素子の構造を示す部分断面図である。
【図４】 本発明の好ましい受光素子の構造を示す部分断面図である。
【図５】 本発明の好ましい受光素子の構造を示す部分断面図である。
【図６】 本発明の好ましい受光素子の構造を示す部分断面図である。
【図７】 本発明の積層型受光素子の一例を示す断面図である。
【図８】 本発明の積層型受光素子の一例を示す断面図である。
【図９】 本発明の積層型受光素子の一例を示す断面図である。
【図１０】 実施例１．における、受光素子組み立ての説明図である。
【図１１】 実施例１．で使用した回転円盤スリットの図である。
【図１２】 実施例１．における受光素子の電流応答を示す図である。
【図１３】 実施例２．における、積層型受光素子組み立ての説明図である。
【図１４】 実施例２．における、積層型受光素子の光電流応答を示す図である。
【図１５】 実施例２．における、積層型受光素子の光電流応答を示す図である。
【図１６】 実施例２．における、積層型受光素子の光電流応答を示す図である。
【符号の説明】
10,10'・・・導電層
10a,10a',10a''・・・透明導電層
11・・・金属リード
20,20'・・・感光層
20B・・・青色感光層
20G・・・緑色感光層
20R・・・赤色感光層
21・・・半導体微粒子
22・・・色素
23・・・電解質材料
30,30'・・・電解質層
40,40'・・・基板
40a,40a',40a'',40a'''・・・透明基板
50,50'・・・下塗り層
60・・・対極
60a,900・・・透明対極
400・・・色素吸着TiO₂層
500・・・スペーサー
510・・・注入口
600・・・青色感光性半導体(BE-1)
700・・・緑色感光性半導体(GE-1)
800・・・赤色感光性半導体(RE-1)[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light receiving element using a semiconductor electrode sensitized with a dye, and more particularly to a light receiving element capable of selectively and immediately extracting only a moving component in an image.
[0002]
[Prior art]
In recent years, the recording density of image information tends to increase more and more with the progress of microfabrication technology and photolithography. However, the development of current high-sensitivity sensors and high-density recording elements is mostly microfabrication technology using silicon as a substrate. Will be borne by the other side. For example, a solid-state device mainly composed of silicon has various functions required for next-generation image processing systems, that is, processing functions necessary for identifying information such as pattern recognition and movement extraction possessed by animal vision. In order to make the solid state element work as a visual information processing system, the burden on the computer side that processes the output information must be increased.
On the other hand, as a so-called differential response type light receiving element having a function of directly converting a change in an optical input signal into an electric signal, a transparent electrode / bacteriorhodopsin thin film / electrolyte / counter electrode configuration (Japanese Patent Laid-Open No. 3-205520), and transparent An electrochemical cell (Japanese Patent Laid-Open No. 11-37838) having a configuration of electrode / electrolyte / silicon substrate is known.
However, the former has the greatest drawback that the sensitivity is very low, and also uses a protein, and thus has a drawback in stability. The latter light receiving element improves the sensitivity, but has the following drawbacks similar to those of the conventional photosensor because of the use of the silicon substrate. First, the precision processing and vapor deposition of Si wafers are required, and the cost is high. Second, the use of silicon is sensitive to infrared light (heat rays), so the S / N ratio for image detection under an indoor dark light source. In that case, an infrared cut filter is required. In addition, any of the light receiving elements is not suitable for use as a color sensor because the choice of spectral wavelength characteristics is small.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a light receiving element excellent in sensitivity and spectral wavelength characteristics. Furthermore, it is providing the image sensor which can identify color information.
[0004]
[Means for Solving the Problems]
As a result of diligent research in view of the above object, the present inventor has found that the conductive layer and two semiconductor electrodes each including a photosensitive layer containing a semiconductor sensitized with a dye are disposed inside the photosensitive layer with the ion conductive electrolyte layer interposed therebetween. It has been found that a light receiving element excellent in sensitivity and spectral wavelength characteristics and an image sensor capable of identifying color information can be obtained by facing each other, and the present invention has been conceived.
[0005]
That is, the light-receiving element of the present invention has two semiconductor electrodes each including a conductive layer and a photosensitive layer containing a semiconductor sensitized with a dye, and an ion conductive electrolyte layer, and the two semiconductor electrodes are ion conductive electrolytes. Facing each other with the photosensitive layer insideAnd the ion conductive electrolyte layer does not contain redox speciesIt is characterized by that.
[0006]
In the light receiving element of the present invention, the two semiconductor electrodes preferably have different photosensitive wavelengths, and the wavelength component of incident light can be detected by the difference in electromotive force generated by the semiconductor electrodes based on the different photosensitive wavelengths. The semiconductor is preferably a metal chalcogenide, TiO₂, ZnO, SnO₂And WO_ThreeMore preferably, it is at least one metal oxide selected from the group consisting of:
[0007]
The image sensor according to the present invention includes a plurality of pixels arranged in units of the light receiving elements.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
[1] Photo detector
Nature (Vol. 353, pp. 737-740, 1991) and US Pat. No. 4927721, etc. describe a photoelectric conversion element using a dye-sensitized oxide semiconductor (hereinafter abbreviated as a dye-sensitized photoelectric conversion element). Has been. This dye-sensitized photoelectric conversion element comprises a photosensitive layer (working electrode) / charge transfer layer / counter electrode on a conductive support, and the photosensitive layer contains a semiconductor having a dye adsorbed on its surface. The charge transfer layer is made of a redox substance, and is responsible for charge transport between the working electrode and the counter electrode by donating electrons to the dye hole generated by photoexcitation charge separation of the dye and accepting electrons on the counter electrode side. As a result, a steady current flows in the circuit between the working electrode and the counter electrode. In such a light receiving element, an optical response current corresponding to a change in the amount of light is output.
[0009]
On the other hand, the light receiving element of the present invention does not have an electron donating action to the dye hole or an electron accepting action from the counter electrode, instead of the charge transfer layer containing the redox substance, unlike the dye-sensitized photoelectric conversion element. Alternatively, an ion conductive electrolyte having no action is used, and a dye-sensitized semiconductor electrode similar to the working electrode is used as the counter electrode. When the light receiving surface of the light receiving element of the present invention is irradiated with light and the dye in one photosensitive layer is excited, electrons are injected from the excited dye into the oxide semiconductor, the electrons pass through the circuit, and the other dye semiconductor electrode Move to the (counter electrode) side. As a result, a dye hole (usually a cation or a cation radical) is generated in the photosensitive layer in which the dye is excited, and a negatively polarized charge separation state is achieved on the counter electrode that is not excited. The anion and cation in the ion conductive electrolyte are polarized to the working electrode side and the counter electrode side so as to stabilize the charge separation state, and an electric double layer is formed on both electrodes. The electric double layer charging current when light irradiation is on and the discharge current when light irradiation is off show a differential response to the light intensity. On the other hand, when the dye in the photosensitive layer on the side different from the above is excited, it polarizes in the opposite polarity as described above, so that a reverse current response is obtained. In other words, the light receiving element of the present invention can be said to be an electric double layer capacitor using light as an electromotive force.
[0010]
Since the polarity of the current response differs depending on which of the two dye-sensitized semiconductor electrodes is photoexcited through the ion conductive electrolyte layer, the color information of the incident light can be obtained, and a single electrochemical element This is a color sensor with two color sensitivities. Since this element transmits light that the photosensitive layer did not absorb, it is possible to create a color sensor that responds to a wider wavelength range by stacking a light-receiving element that contains another color-sensitive photosensitive layer. It becomes. For example, in order to provide a color sensor that covers the visible region, a semiconductor electrode including a blue photosensitive layer, an ion conductive electrolyte layer, and a light transmission layer are disposed on the incident light side of the light receiving element of the present invention including a green photosensitive layer and a red photosensitive layer. A light receiving element comprising a conductive counter electrode, or a semiconductor electrode including a red photosensitive layer on the opposite side of the light receiving element of the present invention including a blue photosensitive layer and a green photosensitive layer, an ion conductive electrolyte layer, and a light transmitting property What is necessary is just to laminate | stack the light receiving element which consists of a counter electrode.
[0011]
As shown in FIG. 1, the light-receiving element of the present invention preferably comprises a conductive layer 10, an undercoat layer 50, a photosensitive layer 20, an ion conductive electrolyte layer 30, a photosensitive layer 20 ′, an undercoat layer 50 ′, and a conductive layer 10 ′. The photosensitive layers 20 and 20 ′ are composed of semiconductor fine particles 21 sensitized by the dye 22 and an electrolyte material 23 that has penetrated into the gaps between the semiconductor fine particles 21. In this case, the photosensitive layers 20 and 20 ′ are preferably sensitized with a dye 22 having different light absorption characteristics. The electrolyte material 23 is composed of the same components as the material used for the ion conductive electrolyte layer 30. Moreover, in order to give intensity | strength to a light receiving element, you may provide the board | substrate 40 and / or 40 'as a base | substrate of the conductive layer 10 and / or 10'. Hereinafter, in the present invention, the layer composed of the conductive layers 10 and 10 ′ and the optional substrates 40 and 40 ′ is referred to as a “conductive support”. Note that the conductive layers 10 and 10 ′ and the substrates 40 and 40 ′ in FIG. 1 may be the transparent conductive layers 10a and 10a ′ and the transparent substrates 40a and 40a ′, respectively.
[0012]
(A) Conductive support
The conductive support is composed of (1) a single layer of a conductive layer, or (2) two layers of a conductive layer and a substrate. In the case of (1), a material that can maintain sufficient strength and sealability is used as the conductive layer, such as a metal material (platinum, gold, silver, copper, zinc, titanium, aluminum, alloys containing these, etc. ) Can be used. In the case of (2), a substrate having a conductive layer containing a conductive agent on the photosensitive layer side can be used. Preferred conductive agents include metals (for example, platinum, gold, silver, copper, zinc, titanium, aluminum, indium, alloys containing these), carbon, and conductive metal oxides (indium-tin composite oxide, tin oxide). And the like doped with fluorine or antimony. The thickness of the conductive layer is preferably about 0.02 to 10 μm.
[0013]
The lower the surface resistance of the conductive support, the better. The surface resistance is preferably 50Ω / □ or less, more preferably 20Ω / □ or less.
[0014]
In order to irradiate light from the conductive support side, the conductive support is preferably substantially transparent. “Substantially transparent” means that the transmittance is 10% or more in a part or all of the light in the visible to near infrared region (400 to 1200 nm), preferably 50% or more, 80% or more is more preferable. In particular, it is preferable that the transmittance in a wavelength region where the photosensitive layer is sensitive is high.
[0015]
The transparent conductive support is preferably formed by applying or vapor-depositing a transparent conductive layer made of a conductive metal oxide on the surface of a transparent substrate such as glass or plastic. The transparent conductive layer is preferably tin dioxide or indium-tin oxide (ITO) doped with fluorine or antimony. As the transparent substrate, a transparent polymer film can be used in addition to a glass substrate such as soda glass which is advantageous in terms of low cost and strength, alkali-free glass which is not affected by alkali elution. The material of the transparent polymer film is, for example, triacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polyester (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyester sulfone (PES), polyimide (PI), polyetherimide (PEI), cyclic polyolefin, brominated phenoxy and the like. In order to ensure sufficient transparency, the amount of conductive metal oxide applied is 1 m of glass or plastic support.²The amount is preferably 0.01 to 100 g.
[0016]
It is preferable to use a metal lead for the purpose of reducing the resistance of the transparent conductive support. The material of the metal lead is preferably platinum, gold, nickel, titanium, aluminum, copper, silver or the like. The metal lead is preferably installed on a transparent substrate by vapor deposition, sputtering or the like, and a transparent conductive layer made of conductive tin oxide, ITO film or the like is preferably provided thereon. The decrease in the amount of incident light due to the installation of the metal lead is preferably within 10%, more preferably 1 to 5%.
[0017]
(B) Photosensitive layer
In the photosensitive layer, the semiconductor acts as a photoconductor, absorbs light, separates charges, and generates electrons and holes. In a dye-sensitized semiconductor, light absorption and the generation of electrons and holes thereby occur mainly in the dye, and the semiconductor fine particles receive and transmit these electrons (or holes). The semiconductor used in the present invention is preferably an n-type semiconductor which gives an anode current by conducting electrons as carriers under photoexcitation.
[0018]
(1) Semiconductor
Semiconductors include simple semiconductors such as silicon and germanium, III-V group compound semiconductors, metal chalcogenides (oxides, sulfides, selenides, composites thereof, etc.), compounds having a perovskite structure (strontium titanate) , Calcium titanate, sodium titanate, barium titanate, potassium niobate, etc.) can be used. Of these, metal chalcogenides are preferred.
[0019]
Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxide, cadmium, zinc, lead, silver, antimony or bismuth. Sulfides, cadmium or lead selenides, cadmium tellurides and the like. Examples of other compound semiconductors include phosphides such as zinc, gallium, indium, and cadmium, gallium-arsenic or copper-indium selenides, and copper-indium sulfides. Furthermore, M_xO_yS_zOr M_1xM_2yO_z (M, M₁And M₂In addition, composites such as are each a metal element, O is oxygen, and x, y, and z are the number of combinations in which the valence is neutral) can be preferably used.
[0020]
The semiconductor used in the present invention is preferably Si, TiO₂, SnO₂, Fe₂O_Three, WO_Three, ZnO, Nb₂O_Five, CdS, ZnS, PbS, Bi₂S_Three, CdSe, CdTe, SrTiO_Three, GaP, InP, GaAs, CuInS₂, CuInSe₂And more preferably TiO₂, ZnO, SnO₂, Fe₂O_Three, WO_Three, Nb₂O_Five, CdS, PbS, CdSe, SrTiO_Three, InP, GaAs, CuInS₂Or CuInSe₂And particularly preferably TiO₂Or Nb₂O_FiveAnd most preferably TiO₂It is. TiO₂TiO containing 70% or more of anatase type crystals₂And particularly preferably 100% anatase type TiO₂It is. It is also effective to dope metals for the purpose of increasing the electronic conductivity in these semiconductors. As a metal to dope, a bivalent or trivalent metal is preferable. In order to prevent a reverse current from flowing from the semiconductor to the ion conductive electrolyte layer, it is also effective to dope the semiconductor with a monovalent metal.
[0021]
The semiconductor used in the present invention may be single crystal or polycrystal, but polycrystal is preferable from the viewpoint of manufacturing cost, securing raw materials, energy payback time, etc., and a porous film made of semiconductor fine particles is particularly preferable. Moreover, a part amorphous part may be included.
[0022]
The particle size of the semiconductor fine particles is generally on the order of nm to μm, but the average particle size of the primary particles obtained from the diameter when the projected area is converted into a circle is preferably 5 to 200 nm, more preferably 8 to 100 nm. preferable. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is preferably 0.01 to 30 μm. Two or more kinds of fine particles having different particle size distributions may be mixed. In this case, the average size of the small particles is preferably 25 nm or less, more preferably 10 nm or less. In order to improve the light capture rate by scattering incident light, it is also preferable to mix semiconductor particles having a large particle size, for example, about 100 to 300 nm.
[0023]
Two or more different types of semiconductor fine particles may be mixed and used. When two or more kinds of semiconductor fine particles are mixed and used, one of them is TiO₂, ZnO, Nb₂O_FiveOr SrTiO_ThreeIt is preferable that The other is SnO₂, Fe₂O_ThreeOr WO_ThreeIt is preferable that A more preferable combination is ZnO and SnO.₂, ZnO and WO_Three, ZnO and SnO₂And WO_ThreeAnd the like. When two or more kinds of semiconductor fine particles are mixed and used, their particle sizes may be different. Especially TiO₂, ZnO, Nb₂O_FiveOr SrTiO_ThreeThe particle size of SnO₂, Fe₂O_ThreeOr WO_ThreeA combination with a small is preferred. Preferably, the large particle size is 100 nm or more, and the small particle size is 15 nm or less.
[0024]
Semiconductor fine particles are prepared by Sakuo Sakuo's “Sol-gel Method Science” Agne Jofusha (1998), Technical Information Association “Sol-gel Method for Thin Film Coating” (1995), etc. The sol-gel method described, Tadao Sugimoto, “Synthesis and size control of monodisperse particles by the new synthesis method gel-sol method”, Materia, Vol. 35, No. 9, pp. 1012-1018 (1996) The gel-sol method described in 1 is preferred. Also preferred is a method developed by Degussa to produce an oxide by high-temperature hydrolysis of chloride in an oxyhydrogen salt.
[0025]
When the semiconductor fine particles are titanium oxide, the sol-gel method, the gel-sol method, and the high-temperature hydrolysis method in the oxyhydrogen salt of chloride are preferred, but Kiyoshi Manabu's “Titanium oxide properties and applied technology” The sulfuric acid method and chlorine method described in Gihodo Publishing (1997) can also be used. Further, as the sol-gel method, the method described in Journal of American Ceramic Society of Barbe et al., Vol. 80, No. 12, pp. 3157-3171 (1997), the chemistry of Burnside et al. , Vol. 10, No. 9, pages 2419-2425 are also preferred.
[0026]
(2) Semiconductor fine particle layer
In order to apply the semiconductor fine particles on the conductive support, in addition to the method of applying a dispersion or colloidal solution of the semiconductor fine particles on the conductive support, the above-described sol-gel method or the like can also be used. Considering mass production of light receiving elements, physical properties of semiconductor fine particle liquid, flexibility of conductive support, etc., a wet film forming method is relatively advantageous. Typical examples of the wet film forming method include a coating method, a printing method, an electrolytic deposition method, and an electrodeposition method. Also, a method of oxidizing metal, a method of depositing in a liquid phase from a metal solution by ligand exchange, etc. (LPD method), a method of vapor deposition by sputtering, a CVD method, or a metal that thermally decomposes on a heated substrate An SPD method in which a metal oxide is formed by spraying an oxide precursor can also be used.
[0027]
In addition to the sol-gel method described above, a method of preparing a dispersion of semiconductor fine particles includes a method of grinding with a mortar, a method of dispersing while grinding using a mill, or a fine particle in a solvent when synthesizing a semiconductor. The method of depositing and using as it is is mentioned.
[0028]
Examples of the dispersion medium include water or various organic solvents (for example, methanol, ethanol, isopropyl alcohol, citronellol, terpineol, dichloromethane, acetone, acetonitrile, ethyl acetate, and the like). At the time of dispersion, for example, a polymer such as polyethylene glycol, hydroxyethyl cellulose, carboxymethyl cellulose, a surfactant, an acid, a chelating agent and the like may be used as a dispersion aid. By changing the molecular weight of polyethylene glycol, the viscosity of the dispersion can be adjusted, and a semiconductor layer that is difficult to peel off can be formed and the porosity of the semiconductor layer can be controlled. Therefore, it is preferable to add polyethylene glycol.
[0029]
As the application method, roller method, dipping method, etc. as application system, air knife method, blade method as metering system, wire that is disclosed in Japanese Patent Publication No. 58-4589 as application and metering can be made the same part The bar method, the slide hopper method, the extrusion method, the curtain method and the like described in U.S. Pat. Nos. 2,681,294, 2,714,419 and 2,767,911, are preferred. A spin method or a spray method is also preferred as a general purpose machine. As the wet printing method, intaglio, rubber plate, screen printing and the like are preferred, including the three major printing methods of letterpress, offset and gravure. From these, a preferred film forming method is selected according to the liquid viscosity and the wet thickness.
[0030]
The layer of semiconductor fine particles is not limited to a single layer, and a multi-layer coating of a dispersion of semiconductor fine particles having different particle sizes, or a multi-layer coating of coating layers containing different types of semiconductor fine particles (or different binders and additives) You can also Multi-layer coating is also effective when the film thickness is insufficient with a single coating.
[0031]
In general, as the thickness of the semiconductor fine particle layer (same as the photosensitive layer thickness) increases, the amount of supported dye increases per unit projected area and the light capture rate increases. Loss due to coupling also increases. Therefore, the preferable thickness of the semiconductor fine particle layer is 0.1 to 100 μm. When used in a photovoltaic cell, the thickness of the semiconductor fine particle layer is preferably 1 to 30 μm, and more preferably 2 to 25 μm. Semiconductor fine particle support 1m²The hit application amount is preferably 0.5 to 100 g, more preferably 3 to 50 g.
[0032]
After the semiconductor fine particles are applied on the conductive support, the semiconductor fine particles are heat-treated in order to bring the semiconductor fine particles into electronic contact with each other and to improve the coating strength and the adhesion to the support. Is preferred. The range of preferable heating temperature is 40-700 degreeC, More preferably, it is 100-600 degreeC. The heating time is about 10 minutes to 10 hours. When using a support having a low melting point or softening point, such as a polymer film, heat treatment is not preferable because it causes deterioration of the support. Further, from the viewpoint of cost, it is preferable to treat at as low a temperature as possible (for example, 50 to 350 ° C.). The temperature can be lowered by heat treatment in the presence of small semiconductor particles of 5 nm or less, mineral acids, and metal oxide precursors, and by applying ultraviolet rays, infrared rays, microwaves, etc., electric fields, and ultrasonic waves. It can also be done. At the same time, in order to remove unnecessary organic substances, it is preferable to use a combination of heating, decompression, oxygen plasma treatment, pure water cleaning, solvent cleaning, gas cleaning and the like in addition to the above irradiation and application.
[0033]
In order to increase the surface area of the semiconductor fine particles after heat treatment, increase the purity in the vicinity of the semiconductor fine particles, and increase the efficiency of electron injection from the dye into the semiconductor fine particles, for example, chemical plating treatment using a titanium tetrachloride aqueous solution or a titanium trichloride aqueous solution You may perform the electrochemical plating process using. In order to prevent a reverse current from flowing from the semiconductor fine particles to the ion conductive electrolyte layer, it is also effective to adsorb an organic substance having a low electron conductivity other than a dye on the particle surface. The organic substance to be adsorbed is preferably one having a hydrophobic group.
[0034]
The semiconductor fine particle layer preferably has a large surface area so that a large amount of dye can be adsorbed. The surface area of the semiconductor fine particle layer coated on the support is preferably at least 10 times, more preferably at least 100 times the projected area. The upper limit is not particularly limited, but is usually about 1000 times.
[0035]
(3) Dye
The sensitizing dye used in the photosensitive layer can be arbitrarily used as long as it is a compound that has absorption in the visible region and near infrared region and can sensitize semiconductors. Organometallic complex dyes, methine dyes, porphyrin dyes, or phthalocyanine dyes A dye is preferred, and an organometallic complex dye is more preferred. In order to widen the wavelength range of photoelectric conversion as much as possible and increase the conversion efficiency, it is preferable to use two or more kinds of dyes in combination or mixed. In this case, it is possible to select the dye to be used or mixed and the ratio thereof so as to match the wavelength range and intensity distribution of the target light source.
[0036]
Such a dye preferably has an appropriate interlocking group capable of adsorbing to the surface of the semiconductor fine particles. Preferred linking groups include COOH groups, OH groups, SO_ThreeH group, -P (O) (OH)₂Group and -OP (O) (OH)₂And chelating groups having π conductivity such as oximes, dioximes, hydroxyquinolines, salicylates and α-ketoenolates. Among them, COOH group, -P (O) (OH)₂Group and -OP (O) (OH)₂The group is particularly preferred. These groups may form a salt with an alkali metal or the like, or may form an internal salt. In the case of a polymethine dye, if the methine chain contains an acidic group as in the case where the methine chain forms a squarylium ring or a croconium ring, this part may be used as a linking group.
[0037]
Hereinafter, preferred sensitizing dyes used in the photosensitive layer will be specifically described.
(a) Organometallic complex dye
When the dye is a metal complex dye, a metal phthalocyanine dye, a metal porphyrin dye, or a ruthenium complex dye is preferable, and a ruthenium complex dye is more preferable. Examples of ruthenium complex dyes include U.S. Pat.Nos. 4,927,721, 4,684,537, 5,844,365, 5,350,644, 5,630,57, 5,525,440, JP-A-7-249790, JP-T-10-504512, WO98 / And complex dyes described in JP 50393 and JP 2000-26487 A.
[0038]
Further, the ruthenium complex dye used in the present invention has the following general formula (I):
(A₁)_pRu (B-a) (B-b) (B-c) (I)
Is preferably represented by: In general formula (I), A₁Represents a mono or bidentate ligand, preferably Cl, SCN, H₂It is a ligand selected from the group consisting of O, Br, I, CN, NCO, SeCN, β-diketone derivatives, oxalic acid derivatives and dithiocarbamic acid derivatives. p is an integer of 0-3. B-a, B-b and B-c are each independently represented by the following formulas B-1 to B-10:
[Chemical 1]

(However, R₁₁Represents a hydrogen atom or a substituent, and examples of the substituent include a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 12 carbon atoms, carbon Examples thereof include substituted or unsubstituted aryl groups having 6 to 12 atoms, the aforementioned acidic groups (these acidic groups may form a salt) and chelating groups. The alkyl portion of the alkyl group and the aralkyl group is The aryl part of the aryl group and the aralkyl group may be monocyclic or polycyclic (fused ring, ring assembly). ) Represents an organic ligand selected from the compounds represented by: B-a, B-b and B-c may be the same or different, and may be any one or two.
[0039]
Although the preferable specific example of an organometallic complex pigment | dye is shown below, this invention is not limited to these.
[0040]
[Chemical formula 2]

[0041]
[Chemical 3]

[0042]
(b) Methine dye
Preferred methine dyes for use in the present invention are polymethine dyes such as cyanine dyes, merocyanine dyes, and squarylium dyes. Examples of polymethine dyes preferably used in the present invention include JP-A-11-35836, JP-A-11-67285, JP-A-11-86916, JP-A-11-97725, JP-A-11-158395, and JP-A-11-158395. 11-163378, JP-A-11-214730, JP-A-11-214731, JP-A-11-238905, JP-A-2000-26487, European Patents 892411, 918441 and 991092 And the described dyes. Specific examples of preferred methine dyes are shown below, but the present invention is not limited thereto.
[0043]
[Formula 4]

[0044]
[Chemical formula 5]

[0045]
(4) Adsorption of dye to semiconductor fine particles
Adsorption of the dye to the semiconductor fine particle film can be performed by immersing a conductive support having a well-dried semiconductor fine particle layer in the dye solution or by applying a dye solution to the semiconductor fine particle layer. In the former case, an immersion method, a dip method, a roller method, an air knife method or the like can be used. In the case of the immersion method, the adsorption of the dye may be performed at room temperature or may be performed by heating and refluxing as described in JP-A-7-249790. Examples of the latter application method include a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, and a spray method. As a solvent for dissolving the dye, alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane, halogenated hydrocarbons ( Dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1 , 3-Dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc.) ), Hydrocarbons (hexane, petroleum ether Benzene, toluene, etc.), and include a mixture of these solvents.
[0046]
The total amount of dye adsorbed is the unit surface area of the porous semiconductor electrode substrate (1 m²) Is preferably 0.01 to 100 mmol. The amount of the dye adsorbed on the semiconductor fine particles is preferably in the range of 0.01 to 1 mmol per 1 g of the semiconductor fine particles. By using such an amount of dye adsorbed, a sensitizing effect in a semiconductor can be sufficiently obtained. On the other hand, if the amount of the dye is too small, the sensitizing effect becomes insufficient, and if the amount of the dye is too large, the dye not attached to the semiconductor floats, which causes a reduction in the sensitizing effect. In order to increase the adsorption amount of the dye, it is preferable to perform a heat treatment before the adsorption. In order to avoid water adsorbing on the surface of the semiconductor fine particles after the heat treatment, it is preferable to quickly perform the dye adsorption operation at a temperature of the semiconductor electrode substrate of 60 to 150 ° C. without returning to normal temperature. Further, for the purpose of reducing the interaction such as aggregation between the dyes, a colorless compound may be added to the dyes and co-adsorbed on the semiconductor fine particles. A compound effective for this purpose is a compound having a surface active property and structure, and examples thereof include a steroid compound having a carboxyl group (for example, chenodeoxycholic acid) or sulfonates such as the following examples.
[0047]
[Chemical 6]

[0048]
The unadsorbed dye is preferably removed by washing immediately after adsorption. Cleaning is preferably performed using a wet cleaning tank and using an organic solvent such as a polar solvent such as acetonitrile or an alcohol solvent. After adsorbing the dye, the surface of the semiconductor fine particles may be treated with an amine or a quaternary salt. The amines are preferably pyridine, 4-t-butylpyridine, polyvinylpyridine and the like, and the quaternary salts are preferably tetrobutylammonium iodide, tetrahexylammonium iodide and the like. When these are liquids, they may be used as they are, or may be used after being dissolved in an organic solvent.
[0049]
(C) Ion conductive electrolyte layer
The electrolyte used in the ion conductive electrolyte layer is not particularly limited as long as it is an ion conductive material, and any conventionally known electrolyte may be used. The type of ions contained in the electrolyte is not particularly limited, but is preferably neither stable nor electron-conducting without being oxidized or reduced at the operating voltage (varies depending on the material and configuration used in the device, but usually 1 V or less). . Examples of typical electrolytes that can be used in the present invention include a solution in which ions are dissolved (electrolytic solution), a so-called gel electrolyte in which an electrolytic solution is impregnated in a gel of a polymer matrix, a molten salt electrolyte, a polymer electrolyte, and an inorganic solid electrolyte. Examples thereof include solid electrolytes such as (conductive ion crystals).
[0050]
(1) Molten salt electrolyte
The molten salt electrolyte is a salt which is liquid at room temperature or has a low melting point. For example, WO95 / 18456, JP-A-8-259543, Electrochemistry, Vol. 65, No. 11, 923 (1997) And the like, known electrolytes such as pyridinium salts, imidazolium salts, and triazolium salts described in the above. The melting point of the molten salt is preferably 100 ° C. or less, and it is particularly preferable that it becomes liquid near room temperature.
[0051]
In the present invention, the following general formulas (Y-a), (Y-b) and (Y-c):
[Chemical 7]

A molten salt represented by any of the above can be preferably used.
[0052]
Q in general formula (Y-a)_y1Represents an atomic group capable of forming a 5- or 6-membered aromatic cation with a nitrogen atom. Q_y1Is preferably composed of one or more atoms selected from the group consisting of carbon atoms, hydrogen atoms, nitrogen atoms, oxygen atoms and sulfur atoms. Q_y1The 5-membered ring formed by is preferably an oxazole ring, thiazole ring, imidazole ring, pyrazole ring, isoxazole ring, thiadiazole ring, oxadiazole ring, triazole ring, indole ring or pyrrole ring, A ring or an imidazole ring is more preferable, and an oxazole ring or an imidazole ring is particularly preferable. Q_y1The 6-membered ring formed by is preferably a pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring or triazine ring, and particularly preferably a pyridine ring.
[0053]
In general formula (Y-b), A_y1Represents a nitrogen atom or a phosphorus atom.
[0054]
X in general formulas (Y-a), (Y-b) and (Y-c)^-Represents an anion, halide ion (Cl^-, Br^-, I^-Etc.), SCN^-, BF_Four ^-, PF₆ ^-, ClO_Four ^-, (CF_ThreeSO₂)₂N^-, (CF_ThreeCF₂SO₂)₂N^-, CH_ThreeSO_Three ^-, CF_ThreeSO_Three ^-, CF_ThreeCOO^-, Ph_FourB^-, (CF_ThreeSO₂)_ThreeC^-Etc. are given as preferred examples, and SCN^-, CF_ThreeSO_Three ^-, CF_ThreeCOO^-, (CF_ThreeSO₂)₂N^-Or BF_Four ^-It is more preferable that
[0055]
R in general formulas (Y-a), (Y-b) and (Y-c)_y1~ R_y11Each independently represents a substituted or unsubstituted alkyl group (preferably having 1 to 24 carbon atoms, which may be linear, branched or cyclic, such as a methyl group, Ethyl group, propyl group, isopropyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, t-octyl group, decyl group, dodecyl group, tetradecyl group, 2-hexyldecyl group, octadecyl group, cyclohexyl group, cyclopentyl Group) or a substituted or unsubstituted alkenyl group (preferably having 2 to 24 carbon atoms, which may be linear or branched, such as a vinyl group or an allyl group). An alkyl group having 2 to 18 carbon atoms or an alkenyl group having 2 to 18 carbon atoms is more preferable, and an alkyl group having 2 to 6 carbon atoms is particularly preferable.
[0056]
In addition, R in the general formula (Y-b)_y2~ R_y5Two or more of them connected to each other_y1May form a non-aromatic ring containing R in the general formula (Y-c)_y6~ R_y11Two or more of them may be connected to each other to form a ring structure.
[0057]
Q above_y1And R_y1~ R_y11May have a substituent. Examples of preferred substituents include halogen atoms (F, Cl, Br, I, etc.), cyano groups, alkoxy groups (methoxy groups, ethoxy groups, methoxyethoxy groups, methoxyethoxyethoxy groups, etc.), aryloxy groups (phenoxy groups, etc.) ), Alkylthio group (such as methylthio group, ethylthio group), alkoxycarbonyl group (such as ethoxycarbonyl group), carbonic acid ester group (such as ethoxycarbonyloxy group), acyl group (acetyl group, propionyl group, benzoyl group, etc.), sulfonyl group (Methanesulfonyl group, benzenesulfonyl group etc.), acyloxy group (acetoxy group, benzoyloxy group etc.), sulfonyloxy group (methanesulfonyloxy group, toluenesulfonyloxy group etc.), phosphonyl group (diethylphosphonyl group etc.), amide Group (acetylamino group, benzoyla Group), carbamoyl group (N, N-dimethylcarbamoyl group, etc.), alkyl group (methyl group, ethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, 2-carboxyethyl group, benzyl group, etc.) Aryl groups (phenyl group, toluyl group, etc.), heterocyclic groups (pyridyl group, imidazolyl group, furanyl group, etc.), alkenyl groups (vinyl group, 1-propenyl group, etc.), silyl groups, silyloxy groups, and the like.
[0058]
The molten salt represented by the general formula (Y-a), (Y-b) or (Y-c) is Q_y1Or R_y1~ R_y11A multimer may be formed via
[0059]
These molten salts may be used alone or in combination of two or more. LiI and CF_ThreeCOOLi, CF_ThreeAlkali metal salts such as COONa, LiSCN and NaSCN can also be added. The addition amount of the alkali metal salt is preferably about 0.02 to 2% by mass, and more preferably 0.1 to 1% by mass.
[0060]
Specific examples of the molten salt preferably used in the present invention are listed below, but are not limited thereto.
[0061]
[Chemical 8]

[0062]
[Chemical 9]

[0063]
[Chemical Formula 10]

[0064]
Embedded image

[0065]
Embedded image

[0066]
Embedded image

[0067]
The molten salt electrolyte is preferably in a molten state at room temperature, and it is preferable not to use a solvent for a composition containing the molten salt electrolyte. Although the solvent described later may be added, the content of the molten salt is preferably 50% by mass or more, and particularly preferably 90% by mass or more with respect to the entire electrolyte composition.
[0068]
(2) Electrolyte
When an electrolytic solution is used for the ion conductive electrolyte layer, the electrolytic solution is preferably composed of an electrolyte salt, a solvent, and an additive.
[0069]
The electrolyte salt is not particularly limited as long as it dissolves in a solvent and ionizes. Specifically, an organic cation or a metal cation (Li⁺, K⁺, Na⁺, Ce²⁺Etc.) and anion X of general formula (Y-a), (Y-b), (Y-c)^-As an example, a preferable electrolyte salt is a combination of
[0070]
The solvent used for the electrolyte is preferably a compound that has low viscosity and improved ion mobility, or has a high dielectric constant and improved effective carrier concentration, and can exhibit excellent ion conductivity. Examples of such solvents include carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether compounds such as dioxane and diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, and polyethylene. Chain ethers such as glycol dialkyl ether and polypropylene glycol dialkyl ether, methanol, ethanol, ethylene glycol monoalkyl ether, alcohols such as propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, ethylene glycol, Propylene glycol, polyethylene glycol, polypropylene glycol , Polyhydric alcohols such as glycerin, nitrile compounds such as acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, benzonitrile, aprotic polar substances such as dimethyl sulfoxide and sulfolane, water and the like. Can also be used.
[0071]
(3) Gel electrolyte
In the present invention, the electrolyte is used by gelling (solidifying) the above-mentioned molten salt electrolyte or electrolyte by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization including polyfunctional monomers, or a crosslinking reaction of the polymer. You can also. In the case of gelation by adding a polymer, compounds described in “Polymer Electrolyte Reviews-1 and 2” (JRMacCallum and CA Vincent co-edited, ELSEVIER APPLIED SCIENCE) can be used. Vinylidene can be preferably used. J. Chem Soc. Japan, Ind. Chem. Sec., 46,779 (1943), J. Am. Chem. Soc., 111,5542 (1989), J. Chem. Soc , Chem. Commun., 1993, 390, Angew. Chem. Int. Ed. Engl., 35, 1949 (1996), Chem. Lett., 1996, 885, J. Chm. Soc., Chem. Commun., The compounds described in 1997,545 can be used, but preferred compounds are those having an amide structure in the molecular structure. An example of gelling the electrolytic solution is described in JP-A No. 11-185863, and an example of gelling the molten salt electrolyte is described in JP-A No. 2000-58140, which can also be applied to the present invention.
[0072]
When the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a crosslinkable reactive group and a crosslinking agent in combination. In this case, preferred crosslinkable reactive groups are amino groups, nitrogen-containing heterocyclic rings (pyridine ring, imidazole ring, thiazole ring, oxazole ring, triazole ring, morpholine ring, piperidine ring, piperazine ring, etc.) and the like. The crosslinking agent is a reagent having two or more functional groups capable of electrophilic reaction with a nitrogen atom (alkyl halide, halogenated aralkyl, sulfonic acid ester, acid anhydride, acid chloride, isocyanate, α, β-unsaturated sulfonyl group, α, β-unsaturated carbonyl group, α, β-unsaturated nitrile group, etc.), and crosslinking techniques described in JP-A Nos. 2000-17076 and 2000-86724 can also be applied.
[0073]
(4) Polymer solid electrolyte
As the polymer compound, a polymer compound that dissolves the electrolyte salt and exhibits ionic conductivity, or a solvent that can dissolve the electrolyte even if the polymer compound itself cannot dissolve the electrolyte is used. Thus, a polymer compound that exhibits ionic conductivity can be used.
[0074]
Examples of the former polymer compound include polyethylene glycol, polyacrylic acid, polymethacrylic acid, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyphosphazene, polysilane, etc., and copolymers thereof in the main chain. A polymer compound having a polyoxyethylene structure in the chain can be used. Even if it is a high molecular compound which can melt | dissolve these electrolytes, the solvent which can melt | dissolve the above-mentioned electrolyte salt can be used together.
[0075]
On the other hand, as an example of the latter polymer compound, polyvinyl chloride, polyacrylonitrile, polyethylene, polypropylene, polyester, polyacrylate, and copolymers thereof can be used. Note that the above-described polymer compound may have a crosslinked structure.
[0076]
(5) Additives in the electrolyte
In the present invention, basic compounds such as tert-butylpyridine, 2-picoline, 2,6-lutidine and the like described in J. Am. Ceram. Soc., 80 (12) 3157-3171 (1997) are also used. It is preferable to add the compound to the aforementioned molten salt electrolyte or electrolytic solution. A preferable concentration range when adding a basic compound is 0.05M to 2M.
[0077]
(6) Formation of ion conductive electrolyte layer
There are two possible methods for forming the ion conductive electrolyte layer. One is a method in which a counter electrode is first bonded on the photosensitive layer, and a liquid electrolyte is sandwiched between the gaps. The other is a method in which an electrolyte is applied directly on the photosensitive layer, and a counter electrode is subsequently applied.
[0078]
In the case of the former method, as a method for sandwiching the electrolyte, a normal pressure process using capillary action due to immersion or the like, or a vacuum process in which the gas phase in the gap is replaced with a liquid phase at a pressure lower than normal pressure can be used.
[0079]
In the case of the latter method, the wet ion conductive electrolyte layer is provided with a counter electrode without being dried, and measures for preventing liquid leakage at the edge portion are taken. In the case of a gel electrolyte, there is a method in which it is applied in a wet manner and solidified by a method such as polymerization. In this case, the counter electrode can be applied after drying and fixing.
[0080]
In the case of a solid electrolyte, an ion conductive electrolyte layer can be formed by a dry film forming process such as a vacuum deposition method or a CVD method, and then a counter electrode can be provided.
[0081]
(D) Undercoat layer
In order to prevent a short circuit between the counter electrode and the conductive support, it is preferable that a dense semiconductor thin film layer is preliminarily applied as an undercoat layer between the conductive support and the photosensitive layer. This method of preventing a short circuit due to the undercoat layer is particularly effective when an electron transport material or a hole transport material is used for the ion conductive electrolyte layer. The undercoat layer is preferably TiO₂, SnO₂, Fe₂O_Three, WO_Three, ZnO or Nb₂O_FiveMore preferably TiO₂Consists of. The undercoat layer can be applied by, for example, a sputtering method in addition to the spray pyrolysis method described in Electrochim. Acta 40, 643-652 (1995). The preferred thickness of the undercoat layer is 5 to 1000 nm, and more preferably 10 to 500 nm.
[0082]
(E) Specific example of internal structure of light receiving element
As described above, the internal structure of the light receiving element can take various forms according to the purpose. If roughly divided into two, a structure that allows light to enter from both sides and a structure that allows only one side are possible. 2 to 6 illustrate the internal structure of a light receiving element that can be preferably applied to the present invention.
[0083]
In FIG. 2, the photosensitive layers 20 and 20 ′ and the ion conductive electrolyte layer 30 are interposed between the transparent conductive layers 10a and 10a ′, and light is incident from both sides. In FIG. 3, a part of the metal lead 11 is provided on the transparent substrate 40a, and further a transparent conductive layer 10a is provided. The undercoat layer 50, the photosensitive layer 20, the ion conductive electrolyte layer 30, the photosensitive layer 20 ′, the undercoat layer 50 ′, In addition, the conductive layer 10 ′ is provided in this order, and the support substrate 40 ′ is further arranged, and light is incident from the transparent substrate 40a side. In FIG. 4, the substrate 40 ′ and the conductive layer 10 ′ of FIG. 3 are replaced with a transparent substrate 40a ′ and a transparent conductive layer 10a ′, and a part of the metal leads 11 is further formed on the transparent substrate 40a ′ and in the transparent conductive layer 10a ′. In this structure, light is incident from both sides. FIG. 5 is a structure in which the undercoat layers 50 and 50 ′ and the metal leads in FIG. 4 are removed, and similarly has a structure in which light enters from both sides. FIG. 6 shows a structure in which the transparent substrate 40a ′ and the transparent conductive layer 10a ′ of FIG. 5 are replaced with the substrate 40 ′ and the conductive layer 10 ′, and light enters from the substrate 40a side.
[0084]
[2] Multilayer color sensor
An example in which the light receiving element of the present invention is applied as a color sensor will be described. This is a plurality of the configuration of the light receiving element of the present invention described in [1], or by combining the configuration of the light receiving element of the present invention with an element configuration having one photosensitive layer of the light receiving element configuration of the present invention as a counter electrode, It has a novel layer structure laminated in the light incident direction. In this case, it is preferable that the photosensitive wavelength region of each photosensitive layer is different.
[0085]
A color optical sensor using the light receiving element of the present invention has a plurality of semiconductor electrodes having different photosensitive wavelength regions and an ion conductive electrolyte layer, and in some cases, has a counter electrode, and has different photosensitive wavelength regions. A plurality of semiconductor electrodes or counter electrodes are laminated with a gap therebetween, and an ion conductive electrolyte layer is filled between the semiconductor electrodes or between the counter electrodes. At the boundary of each layer, the components of each layer may be diffusively mixed with each other.
[0086]
The semiconductor electrode and the ion conductive electrolyte layer used here can be the same as those described in [1] above.
[0087]
The counter electrode used here may have a single-layer structure of a counter electrode conductive layer made of a conductive material, or may be composed of a counter electrode conductive layer and a support substrate, in the same manner as the above conductive support. As the conductive material used for the counter electrode conductive layer, metal (platinum, gold, silver, copper, aluminum, magnesium, indium, etc.), carbon, or conductive metal oxide (indium-tin composite oxide, fluorine-doped tin oxide, etc.) Is mentioned. Among these, platinum, gold, silver, copper, aluminum, or magnesium can be preferably used as the counter electrode layer. An example of a preferable support substrate for the counter electrode is glass or plastic, and the above-described conductive agent is applied or vapor-deposited on the glass or plastic. The thickness of the counter electrode conductive layer is not particularly limited, but is preferably 3 to 10 nm. The lower the surface resistance of the counter electrode layer, the better. The range of the surface resistance is preferably 50Ω / □ or less, more preferably 20Ω / □ or less.
[0088]
The counter electrode may be formed by directly applying, plating or vapor-depositing (PVD, CVD) a conductive material on the ion conductive electrolyte layer, or attaching the conductive layer side of the substrate having the conductive layer. Further, as in the case of the conductive support, it is preferable to use a metal lead for the purpose of reducing the resistance of the counter electrode, particularly when the counter electrode is transparent. In addition, the material and installation method of a preferable metal lead, the fall of the incident light amount by metal lead installation, etc. are the same as the case of an electroconductive support body.
[0089]
In addition, depending on the installation environment, the functionality of a protective layer, an antireflection layer, etc., on the outer surface of one or both of the conductive support and the counter electrode acting as an electrode, between the conductive layer and the substrate, or between the substrates A layer may be provided. For forming these functional layers, a coating method, a vapor deposition method, a bonding method, or the like can be used depending on the material.
A plurality of counter electrodes may be provided corresponding to semiconductor electrodes having different photosensitive wavelength regions, or only one layer of a common counter electrode common to the plurality of semiconductor electrodes may be provided. In the latter case, since all of the plurality of semiconductor electrodes need to be in electrical contact with the counter electrode via the ion conductive electrolyte layer, a charge transfer leak hole is provided in the semiconductor electrode and / or the counter electrode.
[0090]
In addition to the configuration of the color photosensor described above, a support may be provided on the conductive layer and / or the counter electrode as necessary in order to impart mechanical strength. A semiconductor electrode (counter electrode) may be provided only on one side of the support, or two layers of semiconductor electrodes (counter electrode) having different photosensitive wavelength regions may be provided on both sides of the support.
[0091]
In the present invention, since it is necessary to allow light to reach all the photosensitive layers of a plurality of semiconductor electrodes having different photosensitive wavelength regions, a conductive layer (for example, a blue photosensitive layer) carrying the above-described semiconductor photosensitive layer (for example, a blue photosensitive layer) is supported. And the support used as needed) must be substantially optically transparent. In addition, the conductive layer and support supporting the other dye-sensitized semiconductor photosensitive layer are also transparent, and the situation where light transmitted through the upper photosensitive layer passes through the conductive layer and reaches the lower photosensitive layer is satisfied. There must be. However, the conductive layer of the lowermost photosensitive layer and the support thereof may be opaque when no photosensitive layer is disposed in the lower layer. Similarly, when the lowermost layer is a counter electrode, the counter electrode and its support may be opaque.
[0092]
In order to improve the spectral characteristics of the color photosensor, it is preferable that each semiconductor electrode has a sharp spectral wavelength characteristic, and at least one layer of the semiconductor electrodes contains semiconductor fine particles adsorbing a dye in the photosensitive layer. Is preferred. Specifically, it is preferable to provide a dye-sensitized semiconductor electrode having strong absorption independently in each of the three wavelength regions of blue (B), green (G), and red (R). In the case of a semiconductor electrode that does not adsorb a dye, a semiconductor having optical absorption in the visible light wavelength region is used for the semiconductor layer. Is effective.
[0093]
Further, in a structure in which semiconductor photosensitive layers having different photosensitive wavelength regions are laminated, it is preferable that the photosensitive wavelengths are arranged in a long wavelength order from the photosensitive layer closest to the light incident side toward the photosensitive layer farthest. When the semiconductor photosensitive layer is composed of three layers, a blue photosensitive layer (B layer), a green photosensitive layer (G layer), and a red photosensitive layer (R layer), the B layer, G layer, and R layer are sequentially arranged from the light incident side. It is preferable to arrange in this order. In this case, even if the B layer and the counter electrode and the G layer and the R layer are each configured via an ion conductive electrolyte, the B layer, the G layer, the R layer, and the counter electrode are configured via an ion conductive electrolyte, respectively. Good.
[0094]
The internal structure of the light receiving element of the present invention can have various forms according to the purpose as shown in FIGS.
[0095]
FIG. 7 shows an example of the simplest configuration based on the present invention, which is an example of a configuration using three layers of semiconductor electrodes and one layer of counter electrode. A transparent blue photosensitive layer 20B is provided on the lower surface of the first transparent substrate 40a, a transparent green photosensitive layer 20G is provided on the upper surface of the second transparent substrate 40a ′, a red photosensitive layer 20R is provided on the lower surface, and a third substrate 40 is provided. A counter electrode 60 is provided on the upper surface of the substrate, and ion conductive electrolyte layers 30 and 30 ′ are filled between the blue photosensitive layer 20B and the green photosensitive layer 20G and between the red photosensitive layer 20R and the counter electrode 60, respectively. . Here, the light enters from the blue photosensitive layer 20B side, partially passes through the blue photosensitive layer 20B, reaches the green photosensitive layer 20G, and then reaches the red photosensitive layer 20R.
[0096]
FIG. 8 shows an example in which the counter electrode of FIG. 7 is arranged in the middle. A transparent blue photosensitive layer 20B is provided on the lower surface of the first transparent substrate 40a, and a transparent counter electrode 60a is provided on the upper surface of the second transparent substrate 40a ′. In addition, a transparent green photosensitive layer 20G is provided on the lower surface, a red photosensitive layer 20R is provided on the third substrate 40, and the green photosensitive layer 20G and the red photosensitive layer 20R are disposed between the blue photosensitive layer 20B and the transparent counter electrode 60a. It is configured to be filled with ion conductive electrolyte layers 30 and 30 ′, respectively.
[0097]
Also, as shown in FIG. 9, the elements from the transparent substrates 40a to 40a ′ and the elements 40a ″ and 40a ′ ″ are assembled, and the transparent substrates 40a ′ and 40a ″ are bonded to form a multilayer element. You can also.
[0098]
The internal structure of the photoelectric conversion type color photosensor using the light receiving element of the present invention is not limited to that shown in FIGS. 7 and 8. For example, the stacking order is changed or two or more semiconductor electrodes are formed. It is also possible to adopt a configuration using
[0099]
In the color light sensor having the above-described configuration, in a semiconductor electrode having a different photosensitive wavelength region, a photocurrent corresponding to the intensity of light in each photosensitive wavelength region is generated between the electrodes facing each other with the electrolyte interposed therebetween. By detecting this with an external circuit, the color (wavelength) of incident light and its intensity can be sensed.
[0100]
By using semiconductor electrodes having different photosensitive wavelength ranges as elements, the above-described photocurrents can be observed for light of different wavelengths, so that it can function as a color photosensor.
[0101]
A color image sensor can be formed by two-dimensionally arranging a plurality of the above-described color photosensors in which a plurality of semiconductor electrodes having different photosensitive wavelength regions are stacked as one pixel. Thereby, two-dimensional image information can be obtained as an electrical signal.
[0102]
An image sensor can improve the spatial resolution of an image by increasing the number of pixels constituting the pixel sensor, that is, the color light sensor as a unit, and can realize a large area. In the configuration of the image sensor, the counter electrodes of all the pixels can be one common counter electrode.
[0103]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
[0104]
Example 1. Differential response type photo detector
1-1 Preparation of titanium dioxide dispersion
Teflon-coated stainless steel vessel with inner volume of 200 ml, titanium dioxide (Nippon Aerosil Degussa P-25) 15 g, water 45 g, dispersant (Aldrich Triton X-100) 1 g, 0.5 mm diameter zirconia beads ( 30 g) (Nikkato Co., Ltd.) was added and dispersed for 2 hours at 1500 rpm using a sand grinder mill (Imex Co.). The zirconia beads were filtered off from the dispersion. In this case, the average particle diameter of titanium dioxide was 25 nm. The particle size at this time was measured with a master sizer manufactured by MALVERN.
[0105]
1-2 TiO adsorbed dye₂Creation of electrode (electrode A)
The above dispersion was applied to the conductive surface side of conductive glass coated with tin oxide doped with fluorine (TCO glass manufactured by Asahi Glass cut into a size of 20 mm × 100 mm) using a glass rod. At this time, an adhesive tape was applied to a part of the conductive surface side (3 mm from the end) as a spacer, and the adhesive tape was applied so that the adhesive tape came to both ends. After application, the adhesive tape was peeled off and air-dried at room temperature for 1 day. Next, this glass is cut into 20 mm × 15 mm, and TiO 2 as shown in FIG.₂The surface was shaved to expose the conductive surface. This glass was put into an electric furnace (Yamato Scientific muffle furnace FP-32 type) and baked at 450 ° C. for 30 minutes. After the glass was taken out and cooled, a blue absorbing dye (DB-1) in ethanol (19 ml) / dimethyl sulfoxide (1 ml) solution (3 × 10^-Fourmol / L) for 3 hours, washed with ethanol, dried naturally, and dye-adsorbed TiO₂A blue photosensitive semiconductor (BE-1) having a layer 400 was prepared. A green photosensitive semiconductor (GE-1) and a red photosensitive semiconductor (RE-1) were prepared in the same manner except that the green absorbing dye (DG-1) and the red absorbing dye (DR-1) were used. The structures of DB-1, DG-1 and DR-1 dyes are shown below.
[0106]
Embedded image

[0107]
1-3 Creation of light receiving element
TiO prepared as described above₂As shown in FIG. 10 (b), a heat-shrinkable resin sheet (manufactured by DuPont, product name FUSABONDO) was thermally fused as a spacer 500 to the conductive surface of the electrode substrate BG-1. Next, GE-1 with heat-sealed spacers and BE-1 prepared above are TiO 2 as shown in FIG.₂The layers were overlapped so as to face each other and heat-sealed while applying pressure. The electrolyte E-101 shown in Table 1 was injected into the gap between the blue photosensitive semiconductor (BE-1) 600 and the green photosensitive semiconductor (GE-1) 700 from the four corner injection holes 510 provided in the spacer 500. . After the injection, the injection ports at the four corners were closed with an epoxy resin to produce a light receiving element BG-101 of the present invention. Other elements BG-102 to 104 and GR-101 to 104, in which the photosensitive semiconductor of the dye-sensitized semiconductor electrode and the electrolyte shown in Table 1 were replaced, were also prepared in the same manner.
[0108]
[Table 1]

[0109]
1-4. Photo-current response measurement of light receiving element
Between the blue photosensitive semiconductor (BE-1) side of the light receiving element (BG-101) created as described above and the lamp (92mW) of the light source, B, G, and R color filters are shown in FIG. The indicated rotating disk slit was placed. The working electrode terminal of the potentiostat was connected to the BE-1 conductive surface of the light receiving element, the counter electrode terminal of the potentiostat and the reference electrode terminal were connected to the GE-1 conductive surface of the light receiving element, and the potential of the potentiostat was set to 0V. While rotating the disk slit at a speed of 300 rpm, B light, G light, and R light were irradiated to the blue photosensitive semiconductor (BE-1) side through the color filter, and the current value was detected.
[0110]
FIG. 12 shows the current response when irradiated with B light, G light, and R light. When B light is irradiated, a positive current response is obtained at the moment when the light receiving surface is irradiated with light, and a negative current response is obtained at the moment when the light is blocked by the slit, as shown in FIG. In this case, a current response opposite to that in the B light irradiation was obtained. In addition, only a slight current response was obtained when irradiated with R light.
[0111]
Table 2 shows the peak value of the current flowing at the moment when light is irradiated from the slit on the light receiving element surface.
[0112]
[Table 2]

[0113]
From the above results, it was revealed that the light receiving element of the present invention is a highly sensitive light receiving element sensitive to two colors of light.
[0114]
Example 2 .Multilayer light receiving element
2-1 Creating a multilayer photo detector
Cut the same conductive glass used in 1-1 to 15mm x 20mm, and heat the heat-shrinkable resin sheet (made by DuPont, product name FUSABONDO) as spacer 500 as shown in Fig. 13 (a). Fused. The blue photosensitive semiconductor (BE-1) 600 prepared in the conductive glass (transparent counter electrode) 900 and 1-2 was superposed as shown in FIG. 13 (b) and heat-sealed while applying pressure. The electrolytic solution E-101 was injected from the injection port 510 provided in the spacer 500, and the injection port was closed with an epoxy resin to produce a blue photosensitive element B-101. Next, as shown in FIG. 13 (c), the element GR-101 prepared in B-101 and 1-3 is composed of a glass surface on the counter electrode side of B-101 and a glass surface on the GE-1 side of GR-101. The stacked glass ridges were bonded with epoxy resin. As a result, BGR-101, a laminated color sensor, was created by laminating blue photosensitive semiconductor (BE-1) 600, transparent counter electrode 900, green photosensitive semiconductor (GE-1) 700, and red photosensitive semiconductor (RE-1) 800. did.
[0115]
2-2 Measurement of photocurrent response of stacked color sensor
Using the multilayer color sensor BGR-1 created above, the current response and GE of BE-1 and the counter electrode when B, G, R light is irradiated from the BE-1 surface in the same manner as 1-4 The current response between -1 and RE-1 was detected independently using two potentiostats.
[0116]
2-3 Photo-current response measurement of multilayer photo detector
14 to 16 show current responses between BE-1 / counter electrode and GE-1 / RE-1 from the moment when the light receiving surface is irradiated with light through the disk slit until the slit is closed. When B light is irradiated, a large positive current response is obtained between BE-1 and the counter electrode. When G light is irradiated, a positive current response is generated between GE-1 and RE-1, and when R light is irradiated, GE A negative current response was obtained between -1 and RE-1. As described above, it was found that with this multilayer light receiving element, a BGR light change can be detected as a differential current response with a very simple configuration.
[0117]
【The invention's effect】
As described above in detail, the light receiving element of the present invention is excellent in sensitivity and spectral wavelength characteristics, and can easily perform dynamic change and contour extraction of an optical image. In addition, it is possible to detect more color information and light dynamic information at the same time by the multilayer structure of the photosensitive layer.
[Brief description of the drawings]
FIG. 1 is a partial sectional view showing a structure of a preferred light receiving element of the present invention.
FIG. 2 is a partial cross-sectional view showing the structure of a preferred light receiving element of the present invention.
FIG. 3 is a partial sectional view showing a structure of a preferred light receiving element of the present invention.
FIG. 4 is a partial cross-sectional view showing the structure of a preferred light receiving element of the present invention.
FIG. 5 is a partial cross-sectional view showing the structure of a preferred light receiving element of the present invention.
FIG. 6 is a partial sectional view showing a structure of a preferable light receiving element of the present invention.
FIG. 7 is a cross-sectional view showing an example of a multilayer light receiving element of the present invention.
FIG. 8 is a cross-sectional view showing an example of a multilayer light receiving element of the present invention.
FIG. 9 is a cross-sectional view showing an example of a multilayer light receiving element of the present invention.
FIG. 10 shows a first embodiment. It is explanatory drawing of assembling of the light receiving element.
FIG. 11 shows a first embodiment. It is a figure of the rotation disk slit used in FIG.
FIG. 12 shows a first embodiment. It is a figure which shows the electric current response of the light receiving element in.
FIG. 13 shows a second embodiment. FIG. 2 is an explanatory diagram of assembling a multilayer light receiving element.
14 shows a second embodiment. FIG. 5 is a diagram showing a photocurrent response of the multilayer light receiving element in FIG.
15 shows a second embodiment. FIG. 5 is a diagram showing a photocurrent response of the multilayer light receiving element in FIG.
FIG. 16 shows a second embodiment. FIG. 5 is a diagram showing a photocurrent response of the multilayer light receiving element in FIG.
[Explanation of symbols]
10,10 '・ ・ ・ Conductive layer
10a, 10a ', 10a' '・ ・ ・ Transparent conductive layer
11 ... Metal lead
20,20 '・ ・ ・ Photosensitive layer
20B ... Blue photosensitive layer
20G ... Green photosensitive layer
20R ... Red photosensitive layer
21 ... Semiconductor fine particles
22 ... Dye
23 ... Electrolyte material
30,30 '・ ・ ・ Electrolyte layer
40,40 '・ ・ ・ Board
40a, 40a ', 40a' ', 40a' '' ・ ・ ・ Transparent substrate
50,50 '... Undercoat layer
60 ... Counter electrode
60a, 900 ・ ・ ・ Transparent counter electrode
400 ・ ・ ・ Dye adsorption TiO₂layer
500 ・ ・ ・ Spacer
510 ・ ・ ・ Inlet
600 ... Blue photosensitive semiconductor (BE-1)
700 ・ ・ ・ Green photosensitive semiconductor (GE-1)
800 ・ ・ ・ Red photosensitive semiconductor (RE-1)

Claims (6)

 In a light receiving element having two semiconductor electrodes each including a conductive layer and a photosensitive layer containing a semiconductor sensitized with a dye, and an ion conductive electrolyte layer, the two semiconductor electrodes sandwich the ion conductive electrolyte layer. A light receiving element, wherein the photosensitive layer is opposed to the inside, and the ion conductive electrolyte layer does not contain a redox species.  2. The light receiving element according to claim 1, wherein the two semiconductor electrodes have different photosensitive wavelengths.  3. The light receiving element according to claim 2, wherein a wavelength component of incident light is detected by a difference in electromotive force generated between the two semiconductor electrodes.  The light receiving element according to claim 1, wherein the semiconductor is a metal chalcogenide. 5. The light receiving element according to claim 4, wherein the two semiconductors are the same and are at least one metal oxide selected from TiO ₂ , ZnO, SnO _2, and WO ₃ .  6. An image sensor, wherein a plurality of pixels each having the light receiving element according to claim 1 as a unit are arranged.

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