JP7618387B2 - Image pickup element and image pickup device - Google Patents

Description

The present invention relates to an imaging element and an imaging device.

In recent years, photoelectric conversion elements having a photoelectric conversion layer containing an organic semiconductor, imaging elements having photoelectric conversion elements, and imaging devices having imaging elements have been developed.

The photoelectric conversion element has a photoelectric conversion layer and a pair of electrodes (anode and cathode) arranged on either side of the photoelectric conversion layer, which extract the electric charges (holes and electrons) generated in the photoelectric conversion layer to the outside (see, for example, Patent Document 1).

US Patent Application Publication No. 2019/0123285

However, there is a need to reduce the number of residual electrons that cause afterimages when capturing video using an imaging device.

Here, residual electrons are electric charges that are observed as a current that continues to flow even after the light is blocked.

One aspect of the present invention aims to provide an imaging element that can reduce the number of residual electrons.

One aspect of the present invention is an imaging device having a photoelectric conversion element in which an anode, a hole transporting buffer layer, a photoelectric conversion layer, an electron transporting buffer layer, and a cathode are sequentially stacked, the photoelectric conversion layer includes a p-type organic semiconductor and an n-type organic semiconductor, and the electron transporting buffer layer is represented by the general formula (1)

（式中、Ａｒは、置換若しくは無置換のアリール基又は置換若しくは無置換のヘテロアリール基であり、Ｒ_１～Ｒ_４は、それぞれ独立に、水素原子、置換若しくは無置換のアルキル基、置換若しくは無置換のアリール基又は置換若しくは無置換のヘテロアリール基である。）
で表される化合物を含み、前記ｐ型有機半導体は、一般式（２）

(In the formula, Ar is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and R ₁ to R ₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.)
The p-type organic semiconductor includes a compound represented by general formula (2):

（式中、Ａｒ^３は、置換若しくは無置換の２個のカルボニルを有する炭化水素環基又は置換若しくは無置換の２個のカルボニルを有する複素環基であり、Ｒ^１～Ｒ^３は、それぞれ独立に、水素原子、重水素原子、置換若しくは無置換の炭素数１～３０のアルキル基、炭素数１～３０のアルコキシ基又は炭素数６～３０のアリール基であり、Ｒ^１とＲ^２は、互いに結合して環を形成していてもよく、Ａｒ^１及びＡｒ^２は、それぞれ独立に、置換若しくは無置換の炭素数６～３０のアリーレン基又は置換若しくは無置換の炭素数３～３０のヘテロアリーレン基であり、Ｇ^１及びＧ^２は、それぞれ独立に、－（ＣＲ^ｄＲ^ｅ）_ｎ－、－Ｔｅ－、－Ｏ－、－Ｓ－、－Ｓｅ－、－ＮＲ^ｆ－、－ＳｉＲ^ｇＲ^ｈ－、－ＳｉＲ^ｇｇＲ^ｈｈ－、－ＧｅＲ^ｉＲ^ｊ－、－ＧｅＲ^ｉｉＲ^ｊｊ－、－（Ｃ（Ｒ^ｍ）＝（Ｃ（Ｒ^ｎ））－、－（Ｃ（Ｒ^ｍｍ）＝（Ｃ（Ｒ^ｎｎ））－又は単結合であり、Ｒ^ｄ、Ｒ^ｅ、Ｒ^ｆ、Ｒ^ｇ、Ｒ^ｈ、Ｒ^ｉ、Ｒ^ｊ、Ｒ^ｍ及びＲ^ｎは、それぞれ独立に、水素原子、ハロゲン原子、置換若しくは無置換の炭素数１～１０のアルキル基又は置換若しくは無置換の炭素数６～１０のアリール基であり、Ｒ^ｇｇ、Ｒ^ｈｈ、Ｒ^ｉｉ、Ｒ^ｊｊ、Ｒ^ｍｍ及びＲ^ｎｎは、それぞれ独立に、置換若しくは無置換の炭素数１～１０のアルキル基又は置換若しくは無置換の炭素数６～１０のアリール基であり、Ｒ^ｇｇとＲ^ｈｈ、Ｒ^ｉｉとＲ^ｊｊ及びＲ^ｍｍとＲ^ｎｎの少なくとも１つは、互いに結合して環を形成しており、－（ＣＲ^ｄＲ^ｅ）_ｎ－におけるｎは１又は２である。）
で表される化合物である。

(In the formula, Ar ³ is a substituted or unsubstituted hydrocarbon ring group having two carbonyls or a substituted or unsubstituted heterocyclic group having two carbonyls; R ¹ to R ³ are each independently a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, or an aryl group having 6 to 30 carbon atoms; R ¹ and R ² may be bonded to each other to form a ring; Ar ¹ and Ar ² are each independently a substituted or unsubstituted arylene group having 6 to 30 carbon atoms or a substituted or unsubstituted heteroarylene group having 3 to 30 carbon atoms; G ¹ and G ² are each independently -(CR ^d R ^e ) _n -, -Te-, -O-, -S-, -Se-, -NR ^f -, -SiR ^g R ^h -, -SiR ^gg R ^hh R d , R ^{e ,} R ^{f , R g} , R ^h , R ⁱ , R ^j , R ^m and R ⁿ are each independently ^a hydrogen atom, a ^halogen atom, a substituted or unsubstituted alkyl group having ¹ to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon ^{atoms, R gg ,} R ^hh , R ⁱⁱ , R ^jj , ^{R mm and R nn are} each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 ^{carbon atoms, and R gg ,} R ^{hh , R} At least one of ⁱⁱ and R ^jj , and at least one of R ^mm and R ⁿⁿ are bonded to each other to form a ring, and n in -(CR ^d R ^e ) _n - is 1 or 2.
It is a compound represented by the formula:

According to one aspect of the present invention, it is possible to provide an imaging element that can reduce the number of residual electrons.

1 is a cross-sectional view illustrating a schematic partial structure of a first example of an image sensor according to an embodiment of the present invention. 11 is a cross-sectional view illustrating a schematic partial structure of a second example of the image sensor according to the present embodiment. FIG. FIG. 11 is a perspective view illustrating a schematic partial structure of a second example of the imaging element according to the present embodiment. 11 is a cross-sectional view illustrating a schematic partial structure of a third example of the image sensor according to the present embodiment. FIG. FIG. 11 is a perspective view illustrating a schematic partial structure of a fourth example of the image sensor according to the present embodiment.

Next, a description of how to implement the present invention will be given with reference to the drawings.

In the following drawings, thicknesses are enlarged to clearly show multiple layers and regions. In addition, in the drawings, parts that are unnecessary for the explanation are omitted in order to clearly explain the form for implementing the present invention. Furthermore, the same reference numerals are used to refer to the same or similar components throughout the specification.

When a part such as a layer, film, region, or plate is said to be "on" another part, this includes cases where the part is "directly on" the other part, and cases where there is another part between the one part and the other part. Conversely, when a part is said to be "directly on" another part, this means that there is no other part between the one part and the other part.

[Image sensor]
FIG. 1 shows a schematic diagram of a partial structure of a first example of an image sensor according to the present embodiment.

The imaging element 400 includes a photoelectric conversion element 200 and a substrate 310.

The photoelectric conversion element 200 is formed by sequentially stacking an anode 10, a hole transporting buffer layer 40, a photoelectric conversion layer 30, an electron transporting buffer layer 45, and a cathode 20 from the substrate 310 side. Here, the cathode 20 is a light-transmitting electrode. Therefore, when light containing light in the green wavelength region (green light) is incident from the cathode 20 side, the green light is absorbed by the photoelectric conversion layer 30 and photoelectrically converted.

Examples of materials constituting the translucent electrode include conductive materials such as indium tin oxide (ITO), indium zinc oxide (IZO), AZO, FTO, SnO ₂ , TiO ₂ , and ZnO ₂ .

The light-transmitting electrode may be formed of a single layer, or may be formed by stacking multiple layers.

The anode 10 may be either a light-transmitting electrode or a light-opaque electrode.

Examples of materials that can be used to form opaque electrodes include metals such as aluminum, copper, gold, and silver, and conductive materials such as polysilicon that has been doped with impurities to provide conductivity.

When forming the anode 10 and cathode 20, various methods can be applied depending on the materials used.

Methods for forming ITO electrodes include, for example, the electron beam method, the sputtering method, the resistance heating deposition method, the chemical reaction method (e.g., the sol-gel method), and the method of applying a dispersion of indium tin oxide.

When forming the anode 10 and cathode 20, treatments such as UV-ozone treatment and plasma treatment may be performed.

Here, the anode 10 is an electrode that collects holes from the charges generated in the photoelectric conversion layer 30. The cathode 20 is an electrode that collects electrons from the charges generated in the photoelectric conversion layer 30.

By applying a bias voltage between the anode 10 and the cathode 20, the holes generated in the photoelectric conversion layer 30 can be moved to the anode 10 and the electrons can be moved to the cathode 20.

Here, the image sensor 400 converts the amount of holes that have moved to the anode 10 into an electrical signal that corresponds to the amount of holes that have moved to the anode 10, and reads it out. This allows the optical signal to be converted into an electrical signal and extracted.

The electron transport buffer layer 45 suppresses the injection of holes from the cathode 20 into the photoelectric conversion layer 30, and also inhibits the movement of holes generated in the photoelectric conversion layer 30 to the cathode 20.

The electron transport buffer layer 45 is represented by the general formula (1)

（式中、Ａｒは、置換若しくは無置換のアリール基又は置換若しくは無置換のヘテロアリール基であり、Ｒ_１～Ｒ_４は、それぞれ独立に、水素原子、置換若しくは無置換のアルキル基、置換若しくは無置換のアリール基又は置換若しくは無置換のヘテロアリール基である。）
で表される化合物を含む。

(In the formula, Ar is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and R ₁ to R ₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.)
The compound includes a compound represented by the formula:

Here, since the compound represented by general formula (1) has a planar structure, it is believed that stacking inside the electron transport buffer layer 45 increases the mobility of electrons in the out-of-plane direction, thereby reducing the number of residual electrons that cause afterimages when capturing moving images.

The aryl group in Ar and R ₁ to R ₄ is a monocyclic, non-fused polycyclic or fused polycyclic aryl group.

Examples of monocyclic aryl groups include phenyl groups.

Examples of non-condensed polycyclic aryl groups include biphenyl, terphenyl, quaterphenyl, quinquephenyl, sexiphenyl, fluoranthenyl, and triphenylenyl groups.

Examples of condensed polycyclic aryl groups include naphthyl, anthryl, phenanthryl, fluorenyl, indenyl, pyrenyl, acetonaphthenyl, bisphenylfluorenyl, and 9-(9-fluorenyl)fluorenyl groups.

The number of ring carbon atoms in the monocyclic, non-condensed polycyclic or condensed polycyclic aryl group is preferably 6 to 50, and more preferably 6 to 40.

The heteroaryl group in Ar and R ₁ to R ₄ is a monocyclic or polycyclic heteroaryl group.

Examples of monocyclic heteroaryl groups include pyrrolyl, imidazolyl, pyrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, furanyl, pyranyl, thienyl, pyridyl, pyrazyl, pyrimidinyl, pyridazinyl, triazinyl, quinolyl, and isoquinolyl groups.

Examples of polycyclic heteroaryl groups include benzo(pyridyl)furanyl, benzofuranyl, benzothienyl, indolyl, carbazolyl, carbolinyl, phenanthridinyl, acridinyl, perimidinyl, phenanthrolinyl, benzoxazolyl, benzothiazolyl, quinoxalyl, benzimidazolyl, pyrazolyl, dibenzofuranyl, and dibenzothienyl groups.

The number of ring carbon atoms in the monocyclic or polycyclic heteroaryl group is preferably 5 to 50, and more preferably 5 to 30.

The alkyl group in R ₁ to R ₄ is a linear, branched or cyclic alkyl group.

Examples of linear alkyl groups include methyl, ethyl, propyl, butyl, octyl, decyl, and pentadecyl groups.

An example of a branched alkyl group is a t-butyl group.

Examples of cyclic alkyl groups include cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl groups.

The linear or branched alkyl group preferably has 1 to 20 carbon atoms, and more preferably has 1 to 10 carbon atoms.

The cyclic alkyl group preferably has 3 to 20 carbon atoms, and more preferably has 3 to 12 carbon atoms.

Examples of the substituents in Ar and R ₁ to R ₄ include a cyano group, a silyl group, a mono-(di- or tri-)alkylsilyl group having 1 to 10 carbon atoms, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, a linear or branched alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 15 ring carbon atoms, an aryloxy group having 6 to 15 ring carbon atoms, an arylcarbonyl group having 6 to 15 ring carbon atoms, a heterocyclyl group having 3 to 32 ring carbon atoms, a mono-(or di-)alkylamino group having 1 to 10 carbon atoms, and a mono-(or di-)arylamino group having 6 to 15 ring carbon atoms.

Specific examples of compounds represented by general formula (1) are shown below.

これらの中でも、撮像素子４００の残留電子数の点で、１，３，５－トリス（１－フェニル－１Ｈ－ベンズイミダゾール－２－イル）ベンゼン（以下、ＴＰＢｉという）が好ましい。

Among these, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (hereinafter referred to as TPBi) is preferable in terms of the number of residual electrons in the imaging element 400 .

Here, TPBi has the chemical formula

で表される化合物である。

It is a compound represented by the formula:

The thickness of the electron transport buffer layer 45 is preferably 1.5 nm or more and less than 10 nm. When the thickness of the electron transport buffer layer 45 is 1.5 nm or more and less than 10 nm, the photoelectric conversion efficiency of the image sensor 400 is improved.

The photoelectric conversion layer 30 includes a p-type organic semiconductor and an n-type organic semiconductor.

When green light is incident on the photoelectric conversion layer 30, excitons are generated. The excitons are separated into holes and electrons, and then the holes move to the anode 10 and the electrons move to the cathode 20. As a result, a current flows through the photoelectric conversion element 200.

The p-type organic semiconductor has the general formula (2)

（式中、Ａｒ^３は、置換若しくは無置換の２個のカルボニルを有する炭化水素環基又は置換若しくは無置換の２個のカルボニルを有する複素環基であり、Ｒ^１～Ｒ^３は、それぞれ独立に、水素原子、重水素原子、置換若しくは無置換の炭素数１～３０のアルキル基、炭素数１～３０のアルコキシ基又は炭素数６～３０のアリール基であり、Ｒ^１とＲ^２は、互いに結合して環を形成していてもよく、Ａｒ^１及びＡｒ^２は、それぞれ独立に、置換若しくは無置換の炭素数６～３０のアリーレン基又は置換若しくは無置換の炭素数３～３０のヘテロアリーレン基であり、Ｇ^１及びＧ^２は、それぞれ独立に、－（ＣＲ^ｄＲ^ｅ）_ｎ－、－Ｔｅ－、－Ｏ－、－Ｓ－、－Ｓｅ－、－ＮＲ^ｆ－、－ＳｉＲ^ｇＲ^ｈ－、－ＳｉＲ^ｇｇＲ^ｈｈ－、－ＧｅＲ^ｉＲ^ｊ－、－ＧｅＲ^ｉｉＲ^ｊｊ－、－（Ｃ（Ｒ^ｍ）＝（Ｃ（Ｒ^ｎ））－、－（Ｃ（Ｒ^ｍｍ）＝（Ｃ（Ｒ^ｎｎ））－又は単結合であり、Ｒ^ｄ、Ｒ^ｅ、Ｒ^ｆ、Ｒ^ｇ、Ｒ^ｈ、Ｒ^ｉ、Ｒ^ｊ、Ｒ^ｍ及びＲ^ｎは、それぞれ独立に、水素原子、ハロゲン原子、置換若しくは無置換の炭素数１～１０のアルキル基又は置換若しくは無置換の炭素数６～１０のアリール基であり、Ｒ^ｇｇ、Ｒ^ｈｈ、Ｒ^ｉｉ、Ｒ^ｊｊ、Ｒ^ｍｍ及びＲ^ｎｎは、それぞれ独立に、置換若しくは無置換の炭素数１～１０のアルキル基又は置換若しくは無置換の炭素数６～１０のアリール基であり、Ｒ^ｇｇとＲ^ｈｈ、Ｒ^ｉｉとＲ^ｊｊ及びＲ^ｍｍとＲ^ｎｎの少なくとも１つは、互いに結合して環を形成しており、－（ＣＲ^ｄＲ^ｅ）_ｎ－におけるｎは１又は２である。）
で表される化合物である（特許文献１参照）。

(In the formula, Ar ³ is a substituted or unsubstituted hydrocarbon ring group having two carbonyls or a substituted or unsubstituted heterocyclic group having two carbonyls; R ¹ to R ³ are each independently a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, or an aryl group having 6 to 30 carbon atoms; R ¹ and R ² may be bonded to each other to form a ring; Ar ¹ and Ar ² are each independently a substituted or unsubstituted arylene group having 6 to 30 carbon atoms or a substituted or unsubstituted heteroarylene group having 3 to 30 carbon atoms; G ¹ and G ² are each independently -(CR ^d R ^e ) _n -, -Te-, -O-, -S-, -Se-, -NR ^f -, -SiR ^g R ^h -, -SiR ^gg R ^hh R d , R ^{e ,} R ^{f , R g} , R ^h , R ⁱ , R ^j , R ^m and R ⁿ are each independently ^a hydrogen atom, a ^halogen atom, a substituted or unsubstituted alkyl group having ¹ to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon ^{atoms, R gg ,} R ^hh , R ⁱⁱ , R ^jj , ^{R mm and R nn are} each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon ^{atoms, R gg , R hh} , ^R At least one of ⁱⁱ and R ^jj , and at least one of R ^mm and R ⁿⁿ are bonded to each other to form a ring, and n in -(CR ^d R ^e ) _n - is 1 or 2.
The compound is represented by the following formula (see Patent Document 1):

Specific examples of compounds represented by general formula (2) are shown below.

これらの中でも、撮像素子４００の光電変換効率の点で、５－（（５－（１０，１０－ｄｉｍｅｔｈｙｌｄｉｂｅｎｚｏ［ｂ，ｅ］［１，４］ａｚａｓｉｌｉｎ－５（１０Ｈ）－ｙｌ）ｔｅｌｌｕｒｏｐｈｅｎ－２－ｙｌ）ｍｅｔｈｙｌｅｎｅ）－１，３－ｄｉｍｅｔｈｙｌ－２－ｔｈｉｏｘｏｄｉｈｙｄｒｏｐｙｒｉｍｉｄｉｎｅ－４，６（１Ｈ，５Ｈ）－ｄｉｏｎｅ（以下、ＧＤＰ１という）が好ましい。

Among these, 5-((5-(10,10-dimethyldibenzo[b,e][1,4]azasilin-5(10H)-yl)tellurophen-2-yl)methylene)-1,3-dimethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione (hereinafter referred to as GDP1) is preferable in terms of photoelectric conversion efficiency of the imaging element 400.

Here, GDP1 is the chemical formula

で表される化合物である。

It is a compound represented by the formula:

The n-type organic semiconductor is not particularly limited as long as it is capable of forming a pn junction with the p-type organic semiconductor, but examples include subphthalocyanine, fullerene and its derivatives, thiophene and its derivatives, etc., and two or more types may be used in combination. Among these, fullerene and/or fullerene derivatives are preferred in terms of the photoelectric conversion efficiency of the photoelectric conversion element 200.

Examples of fullerenes include _C50 fullerene, _C60 fullerene, _C70 fullerene, _C76 fullerene, _C78 fullerene, _C80 fullerene, _C82 fullerene, _C84 fullerene, _C90 fullerene, _C96 fullerene, _C240 fullerene, and _C540 fullerene.

In fullerene derivatives, fullerene is substituted with a substituent.

Examples of the substituent include an alkyl group, an aryl group, and a heterocyclic group.

The alkyl group may be linear, branched or cyclic.

Examples of linear alkyl groups include methyl, ethyl, propyl, butyl, octyl, decyl, and pentadecyl groups.

An example of a branched alkyl group is a t-butyl group.

Examples of cyclic alkyl groups include cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl groups.

The linear or branched alkyl group preferably has 1 to 20 carbon atoms, and more preferably has 1 to 10 carbon atoms.

The cyclic alkyl group preferably has 3 to 20 carbon atoms, and more preferably has 3 to 12 carbon atoms.

The aryl group is a monocyclic, non-fused polycyclic or fused polycyclic aryl group.

Examples of monocyclic aryl groups include phenyl groups.

Examples of non-condensed polycyclic aryl groups include biphenyl, terphenyl, quaterphenyl, quinquephenyl, sexiphenyl, fluoranthenyl, and triphenylenyl groups.

Examples of condensed polycyclic aryl groups include naphthyl, anthryl, phenanthryl, fluorenyl, indenyl, pyrenyl, acetonaphthenyl, bisphenylfluorenyl, and 9-(9-fluorenyl)fluorenyl groups.

The number of ring carbon atoms in the monocyclic, non-condensed polycyclic or condensed polycyclic aryl group is preferably 6 to 50, and more preferably 6 to 40.

The heterocyclic group is a monocyclic or polycyclic heterocyclic group.

Examples of monocyclic heterocyclic groups include pyrrolyl, imidazolyl, pyrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, furanyl, pyranyl, thienyl, pyridyl, pyrazyl, pyrimidinyl, pyridazinyl, triazinyl, quinolyl, and isoquinolyl groups.

Examples of polycyclic heterocyclic groups include benzo(pyridyl)furanyl groups, benzofuranyl groups, benzothienyl groups, indolyl groups, carbazolyl groups, carbolinyl groups, phenanthridinyl groups, acridinyl groups, perimidinyl groups, phenanthrolinyl groups, benzoxazolyl groups, benzothiazolyl groups, quinoxalyl groups, benzimidazolyl groups, pyrazolyl groups, dibenzofuranyl groups, and dibenzothienyl groups.

The number of ring carbon atoms in the monocyclic or polycyclic heterocyclic group is preferably 5 to 50, and more preferably 5 to 30.

The photoelectric conversion layer 30 may be formed of a single layer, or may be a laminate of multiple layers.

An example of a photoelectric conversion layer 30 formed of a single layer is an intrinsic semiconductor layer.

Examples of the layered structure of the photoelectric conversion layer 30 in which multiple layers are stacked include a p-type semiconductor layer/intrinsic semiconductor layer, an intrinsic semiconductor layer/n-type semiconductor layer, a p-type semiconductor layer/intrinsic semiconductor layer/n-type semiconductor layer, and a p-type semiconductor layer/n-type semiconductor layer.

Here, the intrinsic semiconductor layer includes a p-type organic semiconductor and an n-type organic semiconductor, the p-type semiconductor layer includes a p-type organic semiconductor, and the n-type semiconductor layer includes an n-type organic semiconductor.

The volume ratio of the p-type organic semiconductor to the n-type organic semiconductor in the intrinsic semiconductor layer is preferably 0.01 to 100, and more preferably 0.02 to 95. This improves the photoelectric conversion efficiency of the photoelectric conversion element 200.

The thickness of the photoelectric conversion layer 30 is preferably 1 nm to 800 nm, and more preferably 5 nm to 500 nm. This improves the photoelectric conversion efficiency of the photoelectric conversion element 200.

The photoelectric conversion layer 30 is preferably formed by a dry film formation method, more preferably by a resistance heating deposition method, but may also be formed by a wet film formation method.

Dry film formation methods include, for example, vacuum deposition methods.

Specific examples of vacuum deposition methods include the electron beam method, sputtering method, and resistance heating deposition method.

Examples of wet film formation methods include solution coating methods.

Examples of solution application methods include casting, spin coating, dip coating, blade coating, wire bar coating, spray coating, inkjet printing, screen printing, offset printing, and letterpress printing.

Specific examples of patterning methods when patterning of the photoelectric conversion layer 30 is required include resist etching and laser removal.

The hole-transporting buffer layer 40 suppresses the injection of electrons from the anode 10 into the photoelectric conversion layer 30, and also inhibits the movement of electrons generated in the photoelectric conversion layer 30 to the anode 10.

Examples of materials constituting the hole transport buffer layer 40 include 4,4'-bis[N-naphthalyl-N-phenylamino]biphenyl (α-NPD), N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), 2-TNATA, 4,4',4"-tris(N-(3-methyl)N-phenylamino)triphenylami ne(MTDATA), 4,4',4"-tris[2-naphthalyl(phenyl)amino]triphenylamine (2-TNATA), 9,9'-(9,9,9',9'-tetramethyl-9H,9'H-[2,2'-bifluorene]-7,7'-diyl)bis(3,6-dimethyl-9H-carbazole) (hereinafter referred to as EB1), etc., and two or more of them may be used in combination. Among these, EB1 is preferred from the viewpoints of reducing the dark current value of the image sensor 400 and heat resistance.

Here, EB1 has the chemical formula

で表される化合物である。

It is a compound represented by the formula:

In place of the photoelectric conversion element 200, a photoelectric conversion element in which a cathode 20, an electron transporting buffer layer 45, a photoelectric conversion layer 30, a hole transporting buffer layer 40, and an anode 10 are stacked in this order from the substrate 310 side may be used. In this case, the anode 10 is a light-transmitting electrode, and the cathode 20 may be either a light-transmitting electrode or a non-light-transmitting electrode.

The substrate 310 is a silicon substrate on which a transfer transistor and a charge storage location 55 are integrated. Here, the charge storage location 55 is electrically connected to the photoelectric conversion element 100, and the information in the charge storage location 55 is transferred by the transfer transistor.

Metal wiring and pads are provided on the substrate 310.

The material that constitutes the metal wiring and pads is not particularly limited as long as it is capable of reducing signal delay, but examples include metals with low resistivity such as aluminum, copper, silver, and alloys of these.

An insulating layer 80 is formed between the photoelectric conversion element 200 and the substrate 310.

Materials constituting the insulating layer 80 include inorganic insulating substances such as silicon oxide and silicon nitride, and materials with low relative dielectric constants (low-k materials) such as SiC, SiCOH, SiCO, and SiOF.

The insulating layer 80 has contact holes that expose the pads and through holes 85 that expose the charge storage locations 55.

In addition, a bandpass filter that transmits only visible light may be provided on the photoelectric conversion element 200.

Figures 2 and 3 show schematic diagrams of a partial structure of a second example of the imaging element of this embodiment.

The imaging element 600 comprises a substrate 310, a lower insulating layer 60, a color filter layer 70, an (upper) insulating layer 80, and a (first) photoelectric conversion element 200.

The substrate 310 is a silicon substrate on which a second photosensitive element 50B that senses light in the blue wavelength region (blue light), a third photosensitive element 50R that senses light in the red wavelength region (red light), a charge storage location 55, and a transfer transistor are integrated. Here, the second photosensitive element 50B and the third photosensitive element 50R are silicon photodiodes.

The (first) photoelectric conversion element 200 is disposed on the second photosensitive element 50B and the third photosensitive element 50R and selectively absorbs green light. The charge storage location 55 is electrically connected to the (first) photoelectric conversion element 200.
The (first) photoelectric conversion element 200 may be disposed on the second photosensitive element 50B or the third photosensitive element 50R.

The color filter layer 70 is formed on the second photosensitive element 50B and includes a blue filter 70B that selectively transmits blue light, and a red filter 70R that is formed on the third photosensitive element 50R and selectively transmits red light.

In FIG. 3, B and R respectively indicate the areas where the second photosensitive element 50B and the third photosensitive element 50R sense blue light and red light, and G indicates the area where the (first) photoelectric conversion element 200 selectively absorbs green light.

The second photosensitive element 50B and the third photosensitive element 50R sense blue light and red light, respectively, and the sensed information is transferred by the transmission transistor. Also, the information in the charge storage location 55 is transferred by the transmission transistor.

Metal wiring and pads are provided on the substrate 310, but the metal wiring and pads may also be provided under the second photosensitive element 50B, the third photosensitive element 50R, and the charge storage location 55.

A lower insulating layer 60 is formed on the substrate 310.

The material constituting the lower insulating layer 60 can be the same as the material constituting the insulating layer 80.

A color filter layer 70 is formed on top of the lower insulating layer 60.

An (upper) insulating layer 80 is formed on top of the color filter layer 70 to remove the steps caused by the color filter layer 70 and to flatten the surface.

The (upper) insulating layer 80 and the lower insulating layer 60 are formed with contact holes that expose the pads and through holes 85 that expose the charge storage locations 55.

A (first) photoelectric conversion element 200 is formed on the (upper) insulating layer 80.

As described above, the (first) photoelectric conversion element 200 is formed by sequentially stacking the anode 10, the hole transport buffer layer 40, the photoelectric conversion layer 30, the electron transport buffer layer 45, and the cathode 20 from the substrate 310 side. Here, the anode 10 and the cathode 20 are translucent electrodes capable of transmitting visible light. Therefore, when light including visible light is incident from the cathode 20 side, the green light is absorbed in the photoelectric conversion layer 30 and photoelectrically converted. On the other hand, the light not absorbed in the photoelectric conversion layer 30 is sensed by the second photosensitive element 50B (or the third photosensitive element 50R) after transmitting the hole transport buffer layer 40, the anode 10, and the blue filter 70B (or the red filter 70R).

In addition, a bandpass filter that transmits only visible light may be provided on the (first) photoelectric conversion element 200.

Figure 4 shows a third example of an imaging element according to this embodiment.

Like the imaging element 600, the imaging element 800 includes a substrate 310, an insulating layer 80, and a (first) photoelectric conversion element 200, and the substrate 310 is integrated with a second photosensitive element 50B, a third photosensitive element 50R, a charge storage location 55, and a transmission transistor.

On the other hand, the imaging element 800 differs from the imaging element 600 in that the second photosensitive element 50B and the third photosensitive element 50R are stacked in a direction perpendicular to the surface of the substrate 310, and the color filter layer 70 is omitted.

The second photosensitive element 50B and the third photosensitive element 50R sense blue light and red light, respectively, depending on the stack depth.

The imaging element 800 can be made compact because it is made up of a stack of the second photosensitive element 50B, the third photosensitive element 50R, and the (first) photoelectric conversion element 200.

Instead of integrating the second photosensitive element 50B and the third photosensitive element 50R on the substrate 310, a second photoelectric conversion element that selectively absorbs blue light and a third photoelectric conversion element that selectively absorbs red light may be disposed on the substrate 310 to stack the (first) photoelectric conversion elements (see FIG. 5). This improves the sensitivity of the imaging element and reduces crosstalk.

Here, G, B, and R respectively indicate roughly the area where the (first) photoelectric conversion element 200 selectively absorbs green light, the area where the second photoelectric conversion element selectively absorbs blue light, and the area where the third photoelectric conversion element selectively absorbs red light.

The second photoelectric conversion element has a photoelectric conversion layer between the anode and the cathode that contains a known organic semiconductor that selectively absorbs blue light, and may further have a hole transport buffer layer and/or an electron transport buffer layer formed thereon, as necessary.

The third photoelectric conversion element has a photoelectric conversion layer between the anode and the cathode that contains a known organic semiconductor that selectively absorbs red light, and may further have a hole transport buffer layer and/or an electron transport buffer layer formed thereon, as necessary.

The order in which the (first) photoelectric conversion element 200, the second photoelectric conversion element, and the third photoelectric conversion element are stacked is not particularly limited.

The imaging element of this embodiment can be applied to various imaging devices such as mobile phones, digital cameras, and digital videos.

The following describes examples of the present invention. However, the technical scope of the present invention is not limited to the following examples.

[Example 1]
Directly on the glass substrate with an ITO film having a thickness of 100 nm, EB1 was deposited by resistance heating deposition so as to have a thickness of 5 nm, forming a hole transporting buffer layer. Next, GDP1 as a p-type organic semiconductor and fullerene C ₆₀ as an n-type organic semiconductor were deposited by resistance heating deposition so as to have a p/n ratio of 1 and a thickness of 100 nm, forming a photoelectric conversion layer. Next, TPBi was deposited by resistance heating deposition so as to have a thickness of 1.5 nm, forming a hole transporting buffer layer. Furthermore, an ITO film was deposited by high frequency magnetron sputtering so as to have a thickness of 10 nm, to obtain a photoelectric conversion element.

The degree of vacuum in the above vacuum processes was set to 4×10 ⁻⁴ Pa or less.

[Examples 2 to 4]
Photoelectric conversion elements were obtained in the same manner as in Example 1, except that TPBi was deposited so that the thicknesses of the hole transporting buffer layers were 2.5 nm, 5 nm, and 10 nm, respectively.

[Comparative Examples 1 to 3]
Photoelectric conversion elements were obtained in the same manner as in Examples 2 to 4, except that dipyrazino[2,3-F:2',3'-H]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (hereinafter referred to as HAT-CN) was used instead of TPBi.

Here, HAT-CN has the chemical formula:

で表される化合物である。

It is a compound represented by the formula:

[Comparative Examples 4 to 6]
Photoelectric conversion elements were obtained in the same manner as in Examples 2 to 4, except that 1,3-bis[5-(4-tert-butylphenyl)-2-[1,3,4]oxadiazolyl]benzene (hereinafter referred to as OXD-7) was used instead of TPBi.

Here, OXD-7 has the chemical formula:

で表される化合物である。

It is a compound represented by the formula:

Next, the number of residual electrons in the photoelectric conversion element, IPCE, was evaluated.

[Number of Residual Electrons in Photoelectric Conversion Element, IPCE]
The photoelectric conversion element was transported to a glove box in which the moisture and oxygen contents were kept at 1 ppm or less without being exposed to the atmosphere. Next, the photoelectric conversion element was sealed in a glass sealing can with a moisture absorbent attached using an ultraviolet curable resin, and then heat-treated at 180° C. for 3 hours.

Using an IPCE measurement system (manufactured by Mac Science), a negative bias of 3 V was applied to the ITO-coated glass substrate side of the photoelectric conversion element, and the number of residual electrons [electrons/33 ms] after the light was turned dark when visible light with an illuminance of 5000 lx was irradiated, and the external quantum efficiency (IPCE) at the maximum value of the photoelectric conversion efficiency for light with wavelengths of 500 nm to 720 nm was measured.

Next, we evaluated the image lag characteristics of the imaging device.

[Image retention characteristics]
After applying the above photoelectric conversion element to an imaging device, a moving image was captured, and the presence or absence of an afterimage was visually evaluated.

The criteria for judging image retention characteristics are as follows:

◯: No afterimage is visible when an object of 30,000 lux is photographed. △: No afterimage is visible when an object of 10,000 lux is photographed, but an afterimage is visible when an object of 30,000 lux is photographed. ×: An afterimage is visible when an object of 10,000 lux is photographed. Table 1 shows the evaluation results of the number of residual electrons in the photoelectric conversion element, IPCE, and the afterimage characteristics of the imaging device.

表１から、実施例１～４の光電変換素子は、残留電子数が少なく、実施例１～４の光電変換素子を有する撮像装置は、残像特性に優れることがわかる。また、実施例１～４の光電変換素子は、ＩＰＣＥが高い。

It can be seen from Table 1 that the photoelectric conversion elements of Examples 1 to 4 have a small number of residual electrons, and the imaging devices having the photoelectric conversion elements of Examples 1 to 4 have excellent afterimage characteristics. In addition, the photoelectric conversion elements of Examples 1 to 4 have a high IPCE.

In contrast, the photoelectric conversion elements of Comparative Examples 1 to 6 have a large number of residual electrons because the electron transport buffer layer does not contain the compound represented by general formula (1), and the image pickup devices having the photoelectric conversion elements of Comparative Examples 1 to 6 have poor image retention characteristics.

REFERENCE SIGNS LIST 10 Anode 20 Cathode 30 Photoelectric conversion layer 40 Hole transport buffer layer 45 Electron transport buffer layer 50B Second photosensitive element 50R Third photosensitive element 70 Color filter layer 70B Blue filter 70R Red filter 200 (First) photoelectric conversion element 400, 600, 800 Imaging element

Claims (10)

The photoelectric conversion element includes an anode, a hole transporting buffer layer, a photoelectric conversion layer, an electron transporting buffer layer, and a cathode, which are sequentially stacked on top of each other;
the photoelectric conversion layer includes a p-type organic semiconductor and an n-type organic semiconductor,
the n-type organic semiconductor is a fullerene and/or a fullerene derivative;
The electron transporting buffer layer is formed of a compound represented by the general formula (1)

(In the formula, Ar is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group, and R ₁ to R ₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.)
The compound includes a compound represented by
The p-type organic semiconductor is represented by the general formula (2):

(In the formula, Ar ³ is a substituted or unsubstituted hydrocarbon ring group having two carbonyls or a substituted or unsubstituted heterocyclic group having two carbonyls; R ¹ to R ³ are each independently a hydrogen atom, a deuterium atom, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, an alkoxy group having 1 to 30 carbon atoms, or an aryl group having 6 to 30 carbon atoms; R ¹ and R ² may be bonded to each other to form a ring; Ar ¹ and Ar ² are each independently a substituted or unsubstituted arylene group having 6 to 30 carbon atoms or a substituted or unsubstituted heteroarylene group having 3 to 30 carbon atoms; G ¹ and G ² are each independently -(CR ^d R ^e ) _n -, -Te-, -O-, -S-, -Se-, -NR ^f -, -SiR ^g R ^h -, -SiR ^gg R ^hh R d , R ^{e ,} R ^{f , R g ,} R ^h , R ⁱ , R ^j , R ^m and R n are each independently ^{a hydrogen} atom, a ^halogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon ^{atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; R gg ,} R ^hh , R ⁱⁱ , R ^jj , R ^mm and ^{R nn} are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 ^{carbon atoms ;} R ^gg and ^{R hh} , R ⁱⁱ and ^R At least one of ^jj , R ^mm and R ⁿⁿ is bonded to each other to form a ring, and n in -(CR ^d R ^e ) _n - is 1 or 2.
An imaging element which is a compound represented by the formula: The image sensor according to claim 1, wherein the compound represented by the general formula (1) is 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene. The image sensor according to claim 1 , wherein the electron transporting buffer layer has a thickness of 1.5 nm or more and less than 10 nm. a substrate on which a second photosensitive element sensitive to light in the blue wavelength region and a third photosensitive element sensitive to light in the red wavelength region are integrated;
4. The imaging element according to claim 1, wherein the photoelectric conversion element is a first photoelectric conversion element arranged on the second photosensitive element and/or the third photosensitive element and selectively absorbs light in the green wavelength region. The imaging device according to claim 4 , wherein the second photosensitive element and the third photosensitive element are stacked in a direction perpendicular to a surface of the substrate. A color filter layer is further provided between the substrate and the first photoelectric conversion element,
the color filter layer includes a blue filter that selectively transmits light in a blue wavelength region and a red filter that selectively transmits light in a red wavelength region;
the blue filter is formed on the second photosensitive element;
The imaging device according to claim 4 , wherein the red filter is formed on the third photosensitive element. the photoelectric conversion element is a first photoelectric conversion element that selectively absorbs light in a green wavelength region,
4. The imaging element according to claim 1, wherein the first photoelectric conversion element, a second photoelectric conversion element that selectively absorbs light in the blue wavelength region, and a third photoelectric conversion element that selectively absorbs light in the red wavelength region are stacked. An imaging device comprising the imaging element according to claim 1 . In the general formula (2),
G ¹ is -(CR ^d R ^e ) _n -, -O-, -S-, -Se-, -NR ^f -, -SiR ^g R ^h -, -SiR ^gg R ^hh -, -GeR ⁱ R ^j -, -GeR ⁱⁱ R ^jj -, -(C(R ^m )═C(R ⁿ ))-, -(C(R ^mm )═C(R ⁿⁿ ))- or a single bond; R ^d , R ^e , R ^f , R ^g , R ^h , R ⁱ , R ^j , R ^m and R ⁿ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms; R ^gg , R ^hh , R ⁱⁱ , R 8. The imaging element according to claim 1, wherein ^jj , R ^mm , and R ⁿⁿ are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms, at least one of R ^gg and R ^hh , R ⁱⁱ and R ^jj , and R ^mm and R ⁿⁿ are bonded to each other to form a ring, and n in -(CR ^d R ^e ) _n - is 1 or 2. In the general formula (1), Ar is a substituted aryl group or a substituted or unsubstituted heteroaryl group.
8. The imaging element according to claim 1 , wherein at least one of R ₁ to R ₄ is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

Images