JP6607381B2 - Method for producing layered perovskite thin film and cavity polariton laser using the same - Google Patents

Description

  The present invention relates to a layered perovskite thin film in which organic layers and inorganic layers are alternately laminated, and particularly relates to a method for producing a layered perovskite thin film excellent in optical properties and a cavity polariton laser using the layered perovskite thin film obtained thereby.

  Currently, in the optical field, there is a layered perovskite thin film in which organic layers and inorganic layers are alternately stacked as a material expected to exhibit high optical properties. It is known that a layered perovskite thin film can be produced by the Langmuir-Blodgett method (LB method), which is one of monomolecular film accumulation methods.

  As a method for producing such a conventional layered perovskite thin film, for example, an organic solvent solution in which an organic ammonium molecule is dissolved is dropped on an aqueous solution surface in which a water-soluble organic ammonium molecule and an inorganic halide are dissolved, and then formed on the aqueous solution surface. There is one in which a monomolecular film is transferred onto a substrate using a Langmuir-Blodgett method (LB method) (see Patent Document 1).

  In addition, as the aqueous solution, there is an aqueous solution in which a first inorganic halide and one or more second inorganic halides made of an alkali metal halide are dissolved (see Patent Document 2).

  In addition, as an example of such a layered perovskite thin film, an exciton polariton switch (see Patent Document 3) has been proposed. Furthermore, optically pumped laser oscillation (see Patent Document 4), lead halide layered perovskite Is a new laser oscillation device (see Non-Patent Document 1) that applies the principle of high-efficiency light emission due to carrier aggregation in organic electroluminescence devices, and light that consists of a thin layer of lead halide perovskite sandwiched between two mirrors A drive laser (see Non-Patent Document 2) has been proposed.

  Furthermore, the possibility of application to a cavity polariton laser as a new laser light source has been suggested (Non-patent Document 3). It has been suggested that a cavity polariton laser can be realized using a layered perovskite thin film formed by driving a chain alkylamine out of a monomolecular film by applying a surface pressure (see Non-Patent Document 4).

  In particular, the cavity polariton laser has an excellent possibility that cannot be obtained by a conventional laser. That is, the conventional laser is a four-level system, and a large amount of light energy (threshold value) is required to form the inversion distribution. On the other hand, a cavity polariton laser spontaneously oscillates a laser beam by utilizing Bose-Einstein condensation (BEC) obtained from the cavity polariton. Therefore, the cavity polariton laser is an epoch-making technique that can be called a thresholdless laser, and its realization is eagerly desired.

JP 2001-323387 A JP 2009-6548 A Republication W002 / 017011 JP 2002-241435 A

https://kaken.nii.ac.jp/d/p/12650016.en.html, KAKEN-Construction and laser oscillation of organic / inorganic heterostructure optical resonator elements using self-organized quantum well materials Number: 12650016, 2000-2001 http://ex-press.jp/lfwj/lfwj-news/lfwj-science-research/2667/, perovskite materials can also be used for lasers | e.x.press, April, 15, 2014, Cambridge http://www.saga-u.ac.jp/kokusai/project_kagaku7.html, Makoto Era, Saga University Project Research Institute (SUPLA), Saga University Nanophotonics Laboratory (2015.4-2018.3) H. Era and Kazuhiro Ema, “Optical Properties of Layered Perovskite Organic-Inorganic Superlattices and Application of Low Threshold Laser”, Laser Society Research Report 447th (2013), 1-5

  However, in the conventional method for producing a layered perovskite thin film (for example, Patent Document 1 and Patent Document 2 described above), an optically homogeneous and high-quality layered perovskite thin film exhibiting sufficient optical characteristics has not been obtained. Therefore, at present, the exciton polariton switch (see Patent Document 3), optically pumped laser oscillation (see Patent Document 4), laser oscillation element (see Non-Patent Document 1), optically driven laser (see Non-Patent Document 2), In addition, various uses such as a cavity polariton laser (see Non-Patent Document 3 and Non-Patent Document 4) have not been put into practical use, and the possibility has been suggested only.

  One cause of this is an operation specific to the Langmuir-Blodgett method (LB method). That is, the Langmuir-Blodgett method (LB method) is a method for efficiently transferring a thin film from a monomolecular film formed on a liquid surface onto a substrate, but a single molecule formed on the liquid surface. If the crystallinity (homogeneity) of the film is insufficient, the quality of the layered perovskite thin film, which is the final product, is deteriorated. As a result, a layered perovskite thin film having an optically uniform quality cannot be obtained.

  For example, in the conventional method for producing a layered perovskite thin film, as shown in Patent Document 1 and Patent Document 2, an organic solvent solution in which an organic ammonium molecule is dissolved is dropped into an aqueous solution in which an inorganic halide is dissolved. After the formation of the monomolecular film, in the production of the layered perovskite thin film in the process of compressing the monomolecular film, the layered perovskite structure is formed via the collapse of the monomolecular film. Therefore, an optically inhomogeneous thin film is formed.

  Further, in the conventional method for producing a layered perovskite thin film, for example, according to the surface pressure-area curve of the monomolecular film obtained by the experiment of Non-Patent Document 4, a simple downward curve is shown. Since no flat region (that is, plateau region) is observed, it is confirmed that the formation of the structure is not completed in the condensation region and a perovskite structure with low homogeneity is formed.

  Application to a cavity polariton laser using a layered perovskite thin film is also expected, but in order to achieve this, strong coupling between photons and excitons (rabi splitting) in the cavity is indispensable. Although large Rabi splitting can be expected, it is very difficult to control the cavity length at the nano level, and as described above, optically sufficient quality layered perovskite thin films have not been obtained. Establishing a method for producing high-quality layered perovskite thin films is the most important issue.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for producing a layered perovskite thin film having excellent optical characteristics and a cavity polariton laser using the same.

  As a result of diligent research on thin film formation using the LB method, the present inventor has found a method for dramatically improving the homogeneity of a thin film formed on a liquid surface, and is a new type of layered material that can achieve the above-described purpose. We have succeeded in finding a method for producing perovskite thin films.

  Thus, the method for producing a layered perovskite thin film disclosed in the present application is a method for producing a layered perovskite thin film having a layered perovskite structure in which an organic layer and an inorganic layer are alternately laminated. The organic solution is dropped into an inorganic halide solution containing an inorganic halide and mixed to obtain a uniformly mixed organic solution by dissolving a chain alkylamine and a short-chain alkylamine, and the organic halide solution is not deposited on the liquid surface of the inorganic halide solution. An inorganic halide containing the heterogeneous organic film by a dropping step for forming a uniform organic film and a pressing speed that is complementarily decreased as the number of carbon atoms in the alkyl chain of the long-chain alkylamine and the short-chain alkylamine is increased or decreased. Pressing the solution laterally along the solution surface to form a monomolecular film on the surface of the inorganic halide solution; and the pressing The monomolecular film formed on the liquid surface by degree, Langmuir - is intended to include a monolayer Utsuto step of taking transferred on a substrate using a Blodgett method.

  As described above, the method for producing a layered perovskite thin film disclosed in the present application includes a mixing step of dissolving a long-chain alkylamine and a short-chain alkylamine in a non-aqueous solvent that does not dissolve in an inorganic solution to obtain a uniformly mixed organic solution; A dropping step of dropping the organic solution into an inorganic halide solution containing an inorganic halide to form a heterogeneous organic film on the liquid surface of the inorganic halide solution; and an alkyl chain of a long-chain alkylamine and a short-chain alkylamine. The inorganic halide solution containing the heterogeneous organic film is pressed laterally along the solution surface by a pressing speed that is complementarily increased as the number of carbon atoms increases or decreases, and on the liquid surface of the inorganic halide solution. A step of forming a monomolecular film on the substrate, and a monomolecule that transfers the monomolecular film formed on the liquid surface by the pressing step onto the substrate using the Langmuir-Blodgett method. An organic solution in which the long-chain alkylamine and the short-chain alkylamine are uniformly dissolved in the mixing step is dropped into the inorganic halide solution in the dropping step, whereby the long-chain alkylamine and the short-chain are included. Both alkylamines are homogeneously dispersed in the inorganic halide solution, and the pressing speed is controlled to decrease as the carbon number of the alkyl chain of the short-chain alkylamine approaches the carbon number of the alkyl chain of the long-chain alkylamine. If the molecular size of the short-chain alkylamine is close to that of the long-chain alkylamine (when the molecular size is relatively large), the short-chain alkylamine is difficult to sink in the inorganic halide solution, but it is pressed at a slow pressing speed. Therefore, it sinks in a state in which it maintains a uniform dispersibility carefully, while the short-chain alkyl When the molecular size of the polymer is significantly different from that of the long-chain alkylamine (in the case of a relatively small molecular size), the short-chain alkylamine tends to sink into the inorganic halide solution, but is pressed at a high pressing speed. Therefore, it quickly and surely sinks while maintaining uniform dispersibility, and in any case, the short-chain alkylamine sinks uniformly and reliably into the inorganic halide solution, and the inorganic halide solution By pressing laterally along the surface, the correspondence of the long chain alkylamine and the short chain alkylamine is maintained from the long chain alkylamine and the short chain alkylamine uniformly dispersed in the inorganic halide solution, The short-chain alkylamine is selectively submerged in the inorganic halide solution and separated from the long-chain alkylamine. A layered perovskite in which the inorganic halide in the inorganic halide solution is sandwiched between the long-chain alkylamine and the short-chain alkylamine by the dispersion of the high-chain alkylamine and the short-chain alkylamine, and the organic layer and the inorganic layer are alternately laminated precisely. A structure is formed, and a layered perovskite thin film with high uniformity and precision is reliably obtained.

  Further, in the method for producing a layered perovskite thin film disclosed in the present application, if necessary, the long-chain alkylamine has an alkyl chain having 16 to 28 carbon atoms, and the short-chain alkylamine is the long-chain alkylamine. Have an alkyl chain having 2 or more carbon atoms less than the carbon number of the alkyl chain contained in. Thus, the long-chain alkylamine has an alkyl chain having 16 to 28 carbon atoms, and the short-chain alkylamine has 2 or more carbon atoms less than the carbon number of the alkyl chain contained in the long-chain alkylamine. Thus, while maintaining the molecular size that the short-chain alkylamine does not dissolve in the aqueous phase (inorganic halide solution), the long-chain alkylamine tends to float on the inorganic halide solution, and the short-chain alkylamine A molecular size relationship is formed in which the alkylamine easily sinks into the inorganic halide solution, and a more optically high quality layered perovskite thin film can be obtained.

Further, in the method for producing a layered perovskite thin film disclosed in the present application, the pressing speed of the pressing step is 1.0 × 10 ⁻²⁰ m ² / (molecule · second) to 4.5 × 10 ^{−20 as} necessary. m ² / (numerator · second). Thus, the pressing speed of the pressing step is 1.0 × 10 ⁻²⁰ m ² / (molecule · second) to 4.5 × 10 ⁻²⁰ m ² / (molecule · second). Depending on the speed, the short chain alkylamine is likely to sink into the inorganic halide solution, and a more optically high quality layered perovskite thin film is obtained.

  Further, the cavity polariton laser disclosed in the present application is laminated on the light emitting layer and has an absorption in the ultraviolet-visible region, and is formed of a layered perovskite thin film manufactured by the method for manufacturing a layered perovskite thin film disclosed in the present application. A micro-resonator structure having a buffer layer made of no Langmuir-Blodgett film and a mirror layer formed on the light emitting layer and the buffer layer and formed of a dielectric mirror and / or a metal mirror. . Thus, the cavity polariton laser disclosed in the present application includes a light emitting layer composed of the layered perovskite thin film, a buffer layer composed of a Langmuir-Blodgett film laminated on the light emitting layer and having no absorption in the ultraviolet-visible region, The optically high-quality layered perovskite thin film described above has a microresonator structure that is laminated on the light emitting layer and the buffer layer and includes a mirror layer formed of a dielectric mirror and / or a metal mirror. The long nano-level control can be easily performed, and a thresholdless laser in which laser light is oscillated spontaneously can be realized.

  In addition, in the cavity polariton laser disclosed in the present application, the stacking interval of the mirror layers is n / 2 of the laser wavelength (n is a natural number), and the light emitting layer is generated between the mirror layer stacks as necessary. It is arranged at a position where the intensity of the standing wave becomes the maximum value. Thus, the stacking interval of the mirror layers is n / 2 of the laser wavelength (n is a natural number), and the light emitting layer is at a position where the intensity of the standing wave generated between the mirror layer stacks becomes the maximum value. Since it is disposed, a laser beam with higher intensity is emitted, and a cavity polariton laser having high optical characteristics can be obtained.

Explanatory drawing which shows the flow of the manufacturing method of the layered perovskite thin film which concerns on 1st Embodiment, and the correlation with the difference in carbon number of the alkyl chain of a long-chain alkylamine and a short-chain alkylamine, and a pressing speed (compression speed) The graph which shows is shown. The absorption spectrum when the layered perovskite thin film obtained in Example 1 is accumulated on the substrate, and the relationship between the accumulated number of layers and the absorption spectrum are shown. The XRD measurement result when the layered perovskite thin film obtained in Example 1 is accumulated on the substrate is shown. The AFM observation result when the layered perovskite thin film obtained in Example 1 is accumulated on the substrate is shown. The surface pressure-area curve (π-A curve) of the monomolecular film formed on the liquid surface for obtaining the layered perovskite thin film obtained in Example 1, the result of the reflection spectrum, and the obtained layered perovskite thin film A photographic image is shown. The block diagram of the cavity polariton laser of Example 2, and the relationship between the measured wavelength and refractive index are shown. The relationship between the wavelength (nm) measured from the cavity polariton laser of Example 2 and a reflectance (%), and the relationship between k and energy (eV) are shown.

(First embodiment)
Hereinafter, the manufacturing method of the layered perovskite thin film which concerns on 1st Embodiment is demonstrated based on FIG.

  In the method for producing a layered perovskite thin film according to this embodiment, first, as shown in FIG. 1 (a-1), a long-chain alkylamine and a short-chain alkylamine are dissolved in a non-aqueous solvent that does not dissolve in an inorganic solution. Obtain a uniformly mixed organic solution (S1: mixing step)

The long-chain alkylamine and the short-chain alkylamine are not particularly limited as long as they are two types of alkylamines having different alkyl chain lengths, but preferably contain a halogen element in order to increase the reactivity. And a halogenated alkylamine represented by the general formula C _n H _{2n + 1} NH ₃ X (where X is a halogen element and n is a natural number).

  Further, the long-chain alkylamine has an alkyl chain having 16 to 28 carbon atoms, and more preferably has an alkyl chain having 16 to 22 carbon atoms. The short-chain alkylamine preferably has an alkyl chain having 2 or more carbon atoms less than the carbon number of the alkyl chain contained in the long-chain alkylamine, and the lower limit of the carbon number is the water phase (inorganic halide solution). The number of carbon atoms of the alkyl chain contained in the short-chain alkylamine is 12 or more from the viewpoint that the short-chain alkylamine does not surely dissolve in the inorganic halide solution. More preferred.

  That is, this short-chain alkylamine is not included in the subject because it has an extremely short alkyl chain, such as methylamine or a derivative thereof, because it easily dissolves in the aqueous phase (inorganic halide solution).

In this respect, as an example of a suitable combination of a long-chain alkylamine and a short-chain alkylamine, long-chain alkylamine is represented by docosylamine hydrobromide (C ₂₂ H ₄₅ NH ₃ Br), and short-chain alkylamine is represented by It can be hexadecylamine hydrobromide (C ₁₆ H ₃₃ NH ₃ Br).

  The non-aqueous solvent that does not dissolve in the inorganic solution is not particularly limited as long as it is a solvent that does not dissolve in water, and examples thereof include toluene, chloroform, and dichloromethane.

  The mixing may be performed with stirring and vibration. Thus, since this organic solution is in a state in which the long-chain alkylamine and the short-chain alkylamine are dissolved in the non-aqueous solvent and uniformly mixed, the long-chain alkylamine and the short-chain alkylamine and the short-chain alkylamine are added even after the subsequent dropping step. The chain alkylamine can be maintained in a very dense state, and as a result, a layered perovskite thin film having a precise perovskite structure can be formed.

  Next, as shown in FIG. 1 (a-2), this organic solution is dropped into an inorganic halide solution containing an inorganic halide to form a heterogeneous organic film on the liquid surface of the inorganic halide solution (S2: (Drip process)

The inorganic halide is not particularly limited as long as it contains a halogen atom, and is represented by the general formula MX ₂ (M represents an alkali metal, a transition metal, or a group IV element, and X represents a halide ion). Can do. M can be selected from the group consisting of Pb, Li, Na, K, Ge, Sn, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Cd, but the final product is a layered perovskite thin film. From the viewpoint of improving the optical characteristics, it is preferable to contain lead (Pb).

  Thus, the lead halide layered perovskite compound composed of lead (Pb) forms a quantum well structure composed of an organic amine dielectric layer and a lead halide semiconductor layer, and is high due to its strong quantum confinement effect. Excitons having binding energy and oscillator strength can be formed. Furthermore, since it exhibits high-efficiency exciton light emission and the possibility of controlling the film thickness at the nanoscale, it is expected to be applied to a cavity polariton laser.

  For this reason, the inorganic halide is preferably lead halide. For example, lead bromide, lead chloride, lead fluoride, or the like can be used. In addition, the inorganic halide solution may be a mixture of a plurality of inorganic halides. For example, in addition to the above lead halide, an alkali metal halide such as sodium bromide, lithium bromide, potassium bromide or the like may be mixed to be inorganic. You may comprise a halide solution.

  About dripping of this organic solution, it is possible at normal temperature, and conditions, such as dripping speed | rate, are not specifically limited. In addition, this non-uniform organic film refers to a state where the liquid surface is covered with a sparsely dispersed film such as floating ink.

  Next, as shown in FIG. 1 (a-3), the heterogeneous organic compound is formed by a pressing speed that is complementarily increased as the carbon number of the alkyl chain of the long-chain alkylamine and the short-chain alkylamine is increased or decreased. An inorganic halide solution containing a film is pressed laterally along the solution surface to form a monomolecular film on the liquid surface of the inorganic halide solution (S3: pressing step).

  This pressing acts in the lateral direction along the solution surface, and this pressing force can be made constant. As shown in FIG. 1B, the pressing speed (also referred to as compression speed) is controlled in contradiction to the magnitude relationship between the carbon numbers of the alkyl chains of the long-chain alkylamine and the short-chain alkylamine.

  That is, the pressing speed (compression speed) is set so as to become slower as the carbon number of the alkyl chain of the short-chain alkylamine approaches the carbon number of the alkyl chain of the long-chain alkylamine. In addition, the carbon number of the alkyl chain of the short-chain alkylamine is set to be faster as the difference from the carbon number of the alkyl chain of the long-chain alkylamine increases.

  As for the relationship between the pressing speed (compression speed) and the temperature, it is preferable to increase the pressing speed as the temperature increases, and conversely to decrease the pressing speed as the temperature decreases.

For example, when the carbon number of the alkyl chain of the long-chain alkylamine is 22 and the carbon number of the short-chain alkylamine is 16 at 20 ° C., the pressing speed is 1.0 × 10 ⁻²⁰ m ² / (molecule Second) to 4.5 × 10 ⁻²⁰ m ² / (molecule · second), more preferably 1.0 × 10 ⁻²⁰ m ² / (molecule · second) to 2.0 × 10. ⁻²⁰ m ² / (molecules · second), particularly preferably 1.7 × 10 ⁻²⁰ m ² / (molecules · second).

  In this way, by adjusting the pressing speed, as shown in FIG. 1 (a-4), the correspondence between the long-chain alkylamine and the short-chain alkylamine is maintained (a state in the vicinity of each other), and the short The chain alkylamine can be selectively submerged (squeezed out) into the inorganic halide solution selectively. As a result, the short-chain alkylamine is selectively and homogeneously separated from the long-chain alkylamine in a state where the correspondence with the long-chain alkylamine is maintained (the state where the short-chain alkylamine is located in the vicinity).

  In this way, as shown in FIG. 1 (a-5), the long-chain alkylamine and the short-chain alkylamine are dispersed in the inorganic halide solution with high homogeneity, and the long-chain alkylamine and An inorganic halide in an inorganic halide solution is sandwiched between short-chain alkylamines, and a layered perovskite structure in which organic layers and inorganic layers are alternately and precisely laminated is formed on the liquid surface. A molecular film is reliably formed.

  In this regard, assuming that a long-chain alkylamine is added dropwise to an inorganic halide solution containing a short-chain alkylamine in advance, the short-chain alkylamine in the inorganic halide solution is dispersed in a non-uniform manner. Therefore, when the long-chain alkylamine is dropped, it is probable whether it can be closely opposed to the short-chain alkylamine, and the homogeneity of the monomolecular film formed on the liquid surface of the inorganic halide solution is It becomes unstable. Once a heterogeneous monomolecular film is formed in this way, a layered perovskite structure is formed via the collapse of the monomolecular film when the monomolecular film is compressed, and an optically heterogeneous thin film is formed. Will be.

  On the other hand, according to the present embodiment, as described above, a monomolecular film having a layered perovskite structure in which organic layers and inorganic layers are alternately and precisely laminated is formed on the liquid surface. In addition, a highly precise monomolecular film is reliably formed.

  Next, the obtained monomolecular film is transferred and laminated on the substrate one layer at a time using the Langmuir-Blodgett method (LB method) (S4: monomolecular film transfer step). Although this board | substrate is not specifically limited, A quartz glass board | substrate (transparent quartz glass) can be used from availability, For example, the quartz glass board | substrate (transparent quartz glass) hydrophobized can be used.

By this lamination, a layered perovskite compound thin film whose thickness and structure can be controlled at the monomolecular layer level can be produced. It has been confirmed that this layered perovskite compound thin film surely has a perovskite structure represented by A ₂ MX ₄ (A is an organic ammonium molecule, and M and X are the same as those described above) (see Examples below). .

  The layered perovskite thin film manufactured according to the above can be applied to various optical devices. As an example of the application, a cavity polariton laser using a layered perovskite thin film manufactured according to the above will be described below.

  A cavity polariton laser according to the present embodiment includes a light emitting layer made of a layered perovskite thin film manufactured by the method for manufacturing a layered perovskite thin film, and a Langmuir-Blodget that is laminated on the light emitting layer and has no absorption in the ultraviolet-visible region. The structure includes a buffer layer made of a film and a mirror layer laminated on the light emitting layer and the buffer layer and formed of a dielectric mirror and / or a metal mirror, and has a microresonator structure.

  The material of the Langmuir-Blodgett film that does not absorb in the ultraviolet-visible region is not particularly limited, and for example, cadmium arachidate can be used. Further, the reflectance of the mirror is preferably adjusted to be 90% to 99.9%.

  With this configuration, the optically high-quality layered perovskite thin film obtained above can be easily controlled at the nano level of the cavity length, realizing a thresholdless laser that spontaneously oscillates laser light. it can.

  Further, the stacking interval of the mirror layers is n / 2 of the laser wavelength (n is a natural number), and the light emitting layer has a position where the intensity of the standing wave generated between the upper and lower stacks of the mirror layer becomes the maximum value. It is preferable to arrange | position in. In this case, laser light with higher intensity is emitted, and a cavity polariton laser having high optical characteristics can be obtained.

  Until now, compound semiconductors such as GaAs have been used for cavity polariton lasers, but they have the drawback of requiring advanced vacuum film formation techniques. On the other hand, if the method for producing a layered perovskite thin film according to the present embodiment is used, it can be easily produced at room temperature and normal pressure, and a great advantage is obtained not only in optical quality but also in terms of cost.

  Examples are shown below, but these examples are merely for illustrating the method for producing a layered perovskite thin film according to the present invention, and do not limit the present invention.

Example 1
Chloroform in which docosylamine hydrobromide (C ₂₂ H ₄₅ NH ₃ Br) and hexadecylamine hydrobromide (C ₁₆ H ₃₃ NH ₃ Br) are dissolved at a molar ratio of 1: 1 (10 ⁻⁴ M): The DMF = 9: 1 solution was developed into a lower layer solution (inorganic halide solution) in which NaBr (0.5 M) and PbBr ₂ (2 × 10 ⁻³ M) were mixed at a liquid temperature and room temperature of 20 ° C. constant.

  The absorption spectrum of the layered perovskite thin film accumulated on the substrate is shown in FIG. A lead bromide-based layered perovskite has a band gap of about 3.2 eV and absorbs light corresponding to the band gap, so that a peak is generally formed at a wavelength of 390 nm. In the absorption spectrum of the layered perovskite thin film accumulated on the substrate, a peak was formed at a wavelength of 390 nm as shown in FIG. 2, so that it was confirmed that a perovskite structure was surely formed on the substrate.

  The XRD measurement results of the layered perovskite thin film accumulated on the substrate are shown in FIG. Since the diffraction peak coincided with the (00n) plane, it was confirmed that a layered perovskite structure was surely formed on the substrate.

  FIG. 4 shows the AFM observation result of the layered perovskite thin film accumulated on the substrate. From the obtained results, it was confirmed that a high-level optically high-quality layered perovskite structure thin film having an average roughness of 1/70 of the wavelength required for the cavity polariton laser was obtained.

(Example 2)
The compression rate dependence of the monomolecular film formed on the liquid surface was measured under the following three cases of experimental conditions. FIG. 5A shows the results of the surface pressure-area curve (π-A curve) and reflection spectrum of the monomolecular film formed on the liquid surface. As a result, when the structure on the water surface was confirmed by the reflection spectrum, it was confirmed that the layered perovskite structure was formed at all speeds.
Compression speed:
5 cm ² / min (0.9 × 10 ⁻²⁰ m ² / (molecule · second))
10 cm ² / min (1.7 × 10 ⁻²⁰ m ² / (molecule · second))
28 cm ² / min (4.8 × 10 ⁻²⁰ m ² / (molecule · second))

When the compression speed is 10 cm ² / min (1.7 × 10 ⁻²⁰ m ² / (molecule · second)), the surface pressure-area curve (π-A curve) rises as a smooth curve, and a homogeneous thin film It was confirmed that was formed.

On the other hand, when the compression speed was increased to 28 cm ² / min (4.8 × 10 ⁻²⁰ m ² / (molecule · second)), a film was formed in the initial stage, but the speed was high. The film was broken too much and a homogeneous film was not formed. In addition, when the compression rate was slowed down and performed at 5 cm ² / min (0.9 × 10 ⁻²⁰ m ² / (molecules · second)), a film was formed at the initial stage. The film was broken and a homogeneous thin film was not formed. This is presumed that a monomolecular film having a small limit area was formed by the alkylamine hydrobromide dissolved in the aqueous phase.

From the structure on the water surface in the reflection spectrum, it was confirmed that the layered perovskite structure was formed at all speeds. Of these, the highest homogeneity was obtained especially when the compression speed was 10 cm ² / min. It was confirmed that a film was formed.

When the compression speed was 10 cm ² / min, a plateau region was observed from the surface pressure-area curve (π-A curve), and then the rise of the surface pressure was confirmed. In the reflection spectrum, a peak corresponding to an exciton band peculiar to lead bromide perovskite was observed in the vicinity of 390 nm from the plateau region, and the peak value was saturated when reaching the condensation region. From this, hexadecylamine hydrobromide (C ₁₆ H ₃₃ NH ₃ Br) is extruded (squeezed out) into the aqueous phase (inorganic halide solution) in the plateau region, and a highly homogeneous perovskite structure is obtained. It was confirmed that the structure formation was completed in the condensation region.

(Example 3)
A cavity polariton laser using the layered perovskite thin film manufactured according to the above was prepared according to the configuration of FIG.

  As shown in FIG. 6A, the cavity polariton laser includes a layered perovskite thin film (60 nm) obtained in Example 1 as a light emitting layer, and a buffer formed of cadmium arachidate stacked on the light emitting layer. It comprised from the LB film | membrane as a layer, and the aluminum mirror as a mirror layer laminated | stacked on the said light emitting layer and the buffer layer. The relationship between the measured wavelength (nm) and the refractive index is shown in FIG. The reflectivity of the aluminum mirror was adjusted to be 90% to 99.9%.

  FIG. 7A shows the relationship between the measured wavelength (nm) and the reflectance (%), and FIG. 7B shows the relationship between k and energy (eV). From the obtained results, it was found that a clear resonance was observed at a reflection angle of 22 degrees, and the Rabi splitting was about 130 meV from this peak splitting value. This confirmed that stable cavity polaritons were generated even at room temperature. Therefore, it was shown that if the obtained layered perovskite thin film is used, a cavity polariton laser (a laser having no threshold in principle) at room temperature can be realized.

Claims (3)

A method for producing a layered perovskite thin film having a layered perovskite structure in which organic layers and inorganic layers are alternately laminated,
A mixing step in which a long-chain alkylamine and a short-chain alkylamine are dissolved in a non-aqueous solvent that does not dissolve in the inorganic solution to obtain a uniformly mixed organic solution;
A dropping step of dropping the organic solution into an inorganic halide solution containing an inorganic halide composed of one kind of halogen element, and forming a heterogeneous organic film on the liquid surface of the inorganic halide solution;
The inorganic halide solution containing the heterogeneous organic film is laterally moved along the solution surface by a pressing speed that is complementarily increased as the carbon number of the alkyl chain of the long-chain alkylamine and the short-chain alkylamine is increased or decreased. Pressing in the direction, forming a monomolecular film on the liquid surface of the inorganic halide solution, and
A method for producing a layered perovskite thin film, comprising: a monomolecular film transfer step of transferring a monomolecular film formed on the liquid surface by the pressing step onto a substrate using a Langmuir Blodget method. In the manufacturing method of the layered perovskite thin film according to claim 1,
The long-chain alkylamine has an alkyl chain having 16 to 28 carbon atoms;
The method for producing a layered perovskite thin film, wherein the short-chain alkylamine has an alkyl chain having 2 or more carbon atoms less than the carbon number of the alkyl chain contained in the long-chain alkylamine. In the manufacturing method of the layered perovskite thin film according to claim 1 or 2,
A pressing speed of the pressing step is 1.0 × 10 ⁻²⁰ m ² / (molecule · second) to 4.5 × 10 ⁻²⁰ m ² / (molecule · second). Production method.