Transparent conductive laminate, solar cell, and method of manufacturing same

Abstract

To provide a solar cell including a transparent conductive laminate which suppresses distortion.SOLUTION: A solar cell includes a resin-made substrate, a crystalline transparent conductive film provided on the resin-made substrate, and a non-crystalline transparent conductive film provided between the resin-made substrate and the crystalline transparent conductive film.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a transparent conductive laminate, a solar cell, and a method for manufacturing the same. More specifically, the present invention relates to a transparent conductive laminate in which distortion of a film substrate caused by a transparent conductive material is suppressed. [Background technology]

[0002] International Publication WO2019 / 182058 describes a technology for obtaining a transparent conductive laminate by sputter coating a transparent conductive material onto a film substrate, and a solar cell including the obtained transparent conductive laminate.

[0003] In recent years, there has been a demand for thinner and lighter solar cells, but making the film substrate thinner makes it more likely that distortion will occur during the solar cell manufacturing process, which is an obstacle to making them thinner. In addition, when a transparent conductive laminate is obtained by sputter coating a film substrate with a transparent conductive material, distortion can occur in the substrate film, and wrinkles can also occur. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication WO2019 / 182058 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a solar cell or the like that includes a transparent conductive laminate with reduced distortion. [Means for solving the problem]

[0006] This invention is based on the finding that when a transparent conductive film is formed on a resin substrate, the transparent conductive film includes a crystalline transparent conductive film and an amorphous transparent conductive film. Then, since the internal stresses of these films are opposite, the internal stresses cancel each other out, effectively preventing distortion of the resin substrate. In particular, by adjusting the internal stresses of these layers, the distortion of the resulting laminate can be effectively suppressed, and a laminate with a uniform film thickness and high-performance elements (solar cells and organic EL) can be obtained.

[0007] The first invention relates to a solar cell. This solar cell is made of a resin substrate, a crystalline transparent conductive film provided on the resin substrate, and The conductive film includes a non-crystalline transparent conductive film provided between the resin substrate and the crystalline transparent conductive film.

[0008] The thickness of the resin substrate is preferably 0.1 μm or more and 100 μm or less, and may be 1 μm or more and 10 μm or less.

[0009] The crystalline transparent conductive film and the non-crystalline transparent conductive film are preferably ITO films.

[0010] It is preferable that the solar cell has a non-crystalline transparent conductive film with a positive internal stress and a crystalline transparent conductive film with a negative internal stress.

[0011] The thickness of the crystalline transparent conductive film is d C Then, d C It is preferable that the thickness is 80 nm or more and 300 nm or less. In addition, the thickness of the amorphous transparent conductive film is d A Then, d A / d C It is preferable that the ratio is 1 / 3 or more and 4 / 3 or less.

[0012] The second invention relates to a method for producing a transparent electrode for a transparent conductive laminate. According to this production method, a transparent conductive laminate can also be obtained. A preferred example of the transparent electrode for a transparent conductive laminate is a transparent electrode for a solar cell. This method includes a step of forming an amorphous transparent conductive film having a positive internal stress on a resin substrate; and forming a crystalline transparent conductive film having a negative internal stress after forming the amorphous transparent conductive film.

[0013] The step of forming the amorphous transparent conductive film is preferably carried out under conditions of 1 Pa or more and 20 Pa or less. Moreover, the step of forming a crystalline transparent conductive film is preferably carried out under conditions of 0.02 Pa or more and 0.5 Pa or less.

[0014] The third invention relates to a transparent conductive laminate. This transparent conductive laminate is A resin substrate and A crystalline transparent conductive film provided on a resin substrate; a non-crystalline transparent conductive film provided between a resin substrate and a crystalline transparent conductive film, The thickness of the resin substrate is 1 μm or more and 10 μm or less, The thickness of the crystalline transparent conductive film is d C Then, d C is between 80nm and 300nm, The thickness of the amorphous transparent conductive film is d A Then, d A / d C is between 1 / 3 and 4 / 3. This transparent conductive laminate can employ each of the elements of the solar cell described above as appropriate. Effect of the Invention

[0015] The present invention can provide a solar cell or the like that includes a transparent conductive laminate with reduced distortion. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a graph, instead of a drawing, showing the results of XRD measurement of a glass / ITO thin film. [Diagram 2]Figure 2 shows the results of measuring the internal stress when the thickness of the ITO-C layer is fixed at 150 nm and the thickness of the ITO-A layer is changed. Figure 2(a) is a graph instead of a drawing showing the relationship between internal stress and ITO-A film thickness. Figure 2(b) is a photograph instead of a drawing showing the appearance of each PEN film. [Diagram 3] Figure 3 is a graph in place of a drawing showing the total light transmittance of the substrates. Figure 3(a) shows the transmittance of a glass / ITO substrate, and Figure 3(b) shows the transmittance of a PEN / ITO substrate. [Figure 4] Figure 4 shows a photograph of the obtained solar cell instead of a drawing. Figure 4(a) shows the cross-sectional structure of the solar cell, and Figure 4(b) shows a photograph of the solar cell. [Diagram 5] Figure 5 is a graph instead of a drawing showing the results of measuring the characteristics of the solar cell obtained in the example. Figure 5(a) shows the current-voltage characteristics of the solar cell, and Figure 5(b) shows the spectral sensitivity characteristics of the solar cell. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the embodiments for carrying out the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and includes appropriate modifications of the embodiments described below within the scope obvious to those skilled in the art.

[0018] The first invention relates to a solar cell. Solar cells are publicly known as described in International Publication WO2019 / 182058. A preferred solar cell is a perovskite solar cell. A flexible solar cell (solar cell film) is also preferred as the solar cell.

[0019] This solar cell is made of a resin substrate, a crystalline transparent conductive film provided on the resin substrate, and The conductive film includes a non-crystalline transparent conductive film provided between the resin substrate and the crystalline transparent conductive film.

[0020] Plastic substrate The resin substrate may be a substrate containing a resin. The resin substrate is preferably a flexible film (resin film). The resin substrate is preferably one that is translucent to at least visible light (light with a wavelength of 400 nm to 800 nm). Examples of materials for the resin substrate include polyethersulfone (PES); polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyolefin resins such as polyethylene (PE), polypropylene (PP) and cyclic polyolefin; polyamide resins; polycarbonate resins; polystyrene resins; polyvinyl alcohol resins; saponified ethylene-vinyl acetate copolymers; polyacrylonitrile resins; acetal resins; polyimide resins; and epoxy resins. These resins may be used alone or in combination of two or more. Among these, polyester resins or polyolefin resins are preferred because of their high heat resistance, low linear expansion coefficient, and low manufacturing cost, and polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) are more preferred.

[0021] The shape of the substrate may be any shape, and is effective for all shapes, for example, plate-like such as flat plate or disk, fibrous, rod-like, cylindrical, prismatic, tubular, spiral, spherical, ring-like, etc., and a porous structure may also be adopted. In the present invention, a plate-like substrate is preferred. The thickness of the substrate is not particularly limited in the present invention, and is preferably 0.1 μm to 100 μm, and more preferably 1 μm to 10 μm. Another example of the thickness of the substrate is 1 μm to 200 μm, may be 2 μm to 50 μm, or may be 10 μm to 100 μm. Even if a conductive film is provided on the substrate, the conductive film is generally thinner than the thickness of the substrate, so the thickness of the substrate may be determined without removing the conductive film.

[0022] Transparent Conductive Film This solar cell has a transparent conductive film on a resin substrate. The conductive film is made of a material such as tin-doped indium oxide (ITO), fluorine-doped indium oxide (FTO), zinc oxide (ZnO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), tin oxide (SnO 2 ), indium oxide (In 2 O 3 ), tungsten oxide (WO 3 ) etc.

[0023] Crystalline transparent conductive film A crystalline transparent conductive film means a transparent conductive film with high crystallinity. Crystallinity can be determined by physical properties such as the presence or absence of halo or peak by XRD and electrical conductivity. Even if a halo is present in the spectrum obtained by XRD analysis, if a peak is present, then a crystalline portion is present. This solar cell has a non-crystalline transparent conductive film provided between a resin substrate and a crystalline transparent conductive film. The substrate, the non-crystalline transparent conductive film, and the crystalline transparent conductive film may be provided in this order. In addition, other films or layers may be formed between them. The crystalline transparent conductive film is preferably a film made of crystalline ITO. The crystalline transparent conductive film may have a non-crystalline portion in part. The crystalline transparent conductive film is preferably one having a negative internal stress. The internal stress can be determined by measuring the radius of curvature or displacement of the substrate, as described below. According to formula (1) described below, when the internal stress is positive, the substrate such as a resin substrate having a transparent conductive film on the upper side becomes concave, and when the internal stress is negative, the substrate such as a resin substrate having a transparent conductive film on the upper side becomes convex. The thickness of the crystalline transparent conductive film is defined as d C Then, d C It is preferable that the thickness is 80 nm or more and 300 nm or less, and may be 100 nm or more and 250 nm or less, or may be 150 nm or more and 250 nm or less.

[0024] Amorphous transparent conductive film The amorphous transparent conductive film does not need to be made entirely of amorphous material, as long as it has a large amount of amorphous parts. The amorphous transparent conductive film may have crystalline parts. It is preferable that the amorphous transparent conductive film has a larger proportion of amorphous parts than the crystalline transparent conductive film. It is also preferable that the internal stress of the amorphous transparent conductive film is positive. It is preferable that the amorphous transparent conductive film is a film made of amorphous ITO. The materials of the amorphous transparent conductive film and the crystalline transparent conductive film may be the same or different materials.

[0025] The thickness of the crystalline transparent conductive film is d C The thickness of the amorphous transparent conductive film is d A Then, d A / d C It is preferable that the ratio is 1 / 3 or more and 4 / 3 or less. A / d C may be between 1 / 3 and 1 / 2, or between 2 / 5 and 4 / 5.

[0026] The internal stress of the crystalline transparent conductive film is σ C The internal stress of the amorphous transparent conductive film is σ A Then, |σ A / σ C is preferably 0.5 or more and 2 or less, may be 0.6 or more and 1.6 or less, may be 0.7 or more and 1.4 or less, may be 0.8 or more and 1.3 or less, may be 0.9 or more and 1.1 or less, and is preferably 0.95 or more and 1.05 or less.

[0027] The transparent conductive laminate includes a resin substrate, a crystalline transparent conductive film provided on the resin substrate, and a non-crystalline transparent conductive film provided between the resin substrate and the crystalline transparent conductive film. This transparent conductive laminate includes a transparent electrode in an element such as a solar cell or an organic electroluminescence (EL) element. A perovskite layer or a known layer may be laminated on these. The solar cell will be described below.

[0028] Solar Cell Next, a solar cell (particularly a perovskite solar cell) including the transparent conductive laminate of the present invention will be described. The solar cell may be a solar cell having a known configuration.

[0029] The perovskite solar cell of the present invention comprises, for example, a transparent electrode, a (hole) blocking layer, a perovskite layer (light absorbing layer), an (electron) blocking layer, and a metal electrode in this order. The (hole) blocking layer and the (electron) blocking layer are optional layers. The order of the (hole) blocking layer, perovskite layer (light absorbing layer), and (electron) blocking layer may be reversed. A surface treatment layer may be provided on any surface of the perovskite layer (light absorbing layer).

[0030] transparent electrode The transparent electrode is a support for the blocking layer and has the function of extracting current from the perovskite layer (light absorbing layer) through the blocking layer, so a conductive substrate is preferable, and a transparent conductive layer having translucency that allows light that contributes to photoelectric conversion to pass through is preferable. The transparent electrode is usually preferably adjusted so that its resistance is 5 to 15 Ω / □. The transparent conductive layer can be obtained by a known film formation method depending on the material to be molded.

[0031] The transparent conductive layer may be covered with a light-transmitting covering body as necessary to protect it from the outside. Examples of the light-transmitting covering body include resin sheets such as fluororesin, polyvinyl chloride, polyimide, etc.; inorganic sheets such as white plate glass, soda glass, etc.; and hybrid sheets made by combining these materials. The thickness of these light-transmitting covering bodies is not particularly limited.

[0032] (Electron) Blocking Layer The (electron) blocking layer is a layer provided to prevent electron leakage, suppress reverse current, and improve solar cell characteristics (particularly photoelectric conversion efficiency). When provided between a transparent electrode and a perovskite layer (light absorbing layer), the (electron) blocking layer is preferably a layer made of a metal oxide such as NiOx or an organic semiconductor such as PEDOT:PSS, and more preferably a layer in which the surface of the transparent electrode is smoothly and densely covered with a p-type semiconductor. When the (electron) blocking layer is provided between a perovskite layer and a metal electrode, a coating type organic semiconductor layer such as Spiro-OMeTAD or PTAA is preferred. "Dense" means that the p-type semiconductor in the (electron) blocking layer is densely packed. Note that pinholes, cracks, etc. may be present as long as the transparent electrode and the (electron) blocking layer are not electrically connected.

[0033] The thickness of the (electron) blocking layer is, for example, 1 to 100 nm. From the viewpoint of the efficiency of electron injection into the electrode, the thickness of the (electron) blocking layer is more preferably 20 nm to 50 nm.

[0034] The (electron) blocking layer is formed on the transparent electrode. When an organic semiconductor is used for the (hole) blocking layer, a commercially available PEDOT:PSS aqueous solution can be spin-coated according to known methods (e.g., Nat. Commun. 2020, 11, 3008, etc.).

[0035] The resulting substrate can then be heated in air or in an inert gas atmosphere to form a denser film.

[0036] The aqueous solution of PEDOT:PSS can be used as it is by filtering a commercially available PEDOT:PSS solution (Heraeus, Clevious P VP.Al 4083) with a 0.45 μm PTFE filter. The conditions for heat drying are preferably a temperature of 30 to 150°C, more preferably 100 to 150°C. Furthermore, the heating conditions are more preferably to heat dry in air, then move to a glove box filled with an inert gas (such as Ar), and further heat dry at 100 to 150°C for about 30 minutes.

[0037] ( Hole blocking layer The (hole) blocking layer is formed to selectively collect electrons from the carriers generated in the perovskite layer (light absorbing layer) and improve the photoelectric conversion efficiency. When the (hole) blocking layer is provided between the transparent electrode and the perovskite layer (light absorbing layer), TiO 2 Layer and SnO 2 The SnO layer can be used because it can be formed at low temperatures. 2 It is preferable to use a layer of SnO 2 A solution of nanoparticles was applied by spin coating, and then heated to about 100 to 150 °C to form a SnO film with a thickness of 20 nm to 80 nm. 2 The layer can be formed densely. The particle concentration during spin coating is 5% by weight or more and 50% by weight or less, and may be 10% by weight or more and 30% by weight or less, or may be 10% by weight or more and 20% by weight or less. The thickness of the (hole) blocking layer is, for example, 10 nm or more and 200 nm or less, and may be 20 nm or more and 100 nm or less, or may be 30 nm or more and 60 nm or less, or may be 30 nm or more and 50 nm or less. When the (hole) blocking layer is provided between the perovskite layer and the metal electrode, fullerene (C 60 A hole-blocking layer such as ZnO or its derivatives may be formed on the perovskite layer by spin coating or vacuum deposition. 60When using a material such as a fluorine-containing compound, it is preferable to form it on the perovskite layer by vacuum deposition. In addition, in order to reduce the contact resistance between the (hole) blocking layer and the electrode to be fabricated on it, a buffer layer such as bathocuproine (BCP) can be formed. 60 The thicknesses of the thin film transistor (TFT) and the buffer layer (BCP) may be 1 to 100 nm and 1 to 50 nm, respectively, but are preferably 10 to 50 nm and 1 to 30 nm, more preferably 20 to 40 nm and 3 to 10 nm, and particularly preferably 20 nm and 8 nm.

[0038] Perovskite layer (light absorbing layer) The perovskite layer (light absorbing layer) in a perovskite solar cell is a layer that absorbs light and transfers excited holes and electrons to perform photoelectric conversion. The perovskite layer (light absorbing layer) contains a perovskite material or a perovskite complex. The perovskite layer may be manufactured based on the method described above. It is preferable to realize mass production of the perovskite layer by roll-to-roll. It is preferable to apply the mixed liquid to the substrate by spin coating, dip coating, screen printing, roll coating, die coating, transfer printing, spraying, slit coating, or the like, preferably by spin coating.

[0039] The perovskite layer preferably contains a compound having a perovskite structure. An example of the compound having a perovskite structure is a compound represented by formula (I). Formula (I) is AM m X n ...(I). And, in formula (I), A is a methylammonium cation (CH 3 NH 3 + ), formamidinium cation (NH 2 CHNH 2 + ) and cesium cation (Cs + ) includes one or more of the following: M is Pb 2+and Sn 2+ It is a metal ion containing either or both of the following: X is F - ,Cl - ,Br - , and I - Any one or more of the following. m is 0.8 to 1.2. n is 2.8 to 3.2.

[0040] From the viewpoint of the balance between light absorption efficiency and exciton diffusion length and the absorption efficiency of light reflected by the transparent electrode, the film thickness of the perovskite layer (light absorption layer) is preferably, for example, 50 to 1000 nm, more preferably 200 to 800 nm. The film thickness of the perovskite layer (light absorption layer) is preferably within the range of 100 to 1000 nm, more preferably within the range of 250 to 500 nm. Specifically, it is preferable that the lower limit of the film thickness of the perovskite layer (light absorption layer) is 100 nm or more (particularly 400 nm or more) and the upper limit is 1000 nm or less (particularly 900 nm or less). The film thickness of the perovskite layer (light absorption layer) is measured by a cross-sectional scanning electron microscope (cross-sectional SEM).

[0041] The flatness of the perovskite layer (light absorbing layer) is preferably such that the height difference is 50 nm or less (-25 nm to +25 nm) in a range of 500 nm x 500 nm in the horizontal direction of the surface measured by a scanning electron microscope, and more preferably such that the height difference is 40 nm or less (-20 nm to +20 nm). This makes it easier to balance the light absorption efficiency and the carrier diffusion length, and the absorption efficiency of the light reflected by the metal electrode can be further improved. The flatness of the perovskite layer (light absorbing layer) is measured by a cross-sectional scanning electron microscope (cross-sectional SEM) of the perovskite layer (light absorbing layer) with an arbitrarily determined measurement point as the reference point, the difference with the largest film thickness within the measurement range as the upper limit, and the difference with the smallest film thickness as the lower limit.

[0042] metal electrode The metal electrode is disposed opposite the transparent electrode and formed on the (hole) or (electron) blocking layer, allowing the exchange of charges with each blocking layer. The metal electrode may be made of a material known in the art, such as platinum, titanium, stainless steel, aluminum, gold, silver, nickel, or alloys thereof. Of these, the metal electrode is preferably made of a material that can be formed by a method such as vapor deposition, since the electrode can be formed in a dry atmosphere. Perovskite solar cells having a layer structure other than those described above can also be manufactured by the same method.

[0043] Organic electroluminescence element (organic EL element) Organic EL elements are publicly known elements, as described in, for example, JP 2017-123352 A and JP 2015-071619 A, and their manufacturing methods are also publicly known. An example of an organic EL element has a substrate, an anode, a cathode, and an organic layer disposed between the anode and the cathode. The organic layer is configured by stacking, in this order from the anode side, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an electron injection layer.

[0044] Method for manufacturing transparent electrode for transparent conductive laminate The second invention relates to a method for producing a transparent electrode for a transparent conductive laminate. Examples of the transparent conductive laminate are the solar cell and organic EL described above, or the laminate constituting them. A preferred example of the transparent electrode for a transparent conductive laminate is a transparent electrode for a solar cell. This method includes the steps of forming an amorphous transparent conductive film having positive internal stress on a resin substrate, and, after forming the amorphous transparent conductive film, forming a crystalline transparent conductive film having negative internal stress.

[0045] A process for forming an amorphous transparent conductive film The step of forming an amorphous transparent conductive film is a step for forming an amorphous transparent conductive film having a positive internal stress on a resin substrate. The process of forming the amorphous transparent conductive film is preferably carried out under conditions of 1 Pa to 20 Pa (2 Pa to 15 Pa, or 2.5 Pa to 10 Pa). The amorphous transparent conductive film can be obtained by sputtering or CVD. This process can be carried out, for example, by using a known sputtering device and adjusting the conditions appropriately.

[0046] A process for forming a crystalline transparent conductive film The process of forming a crystalline transparent conductive film is a process for forming a crystalline transparent conductive film having a negative internal stress after forming a non-crystalline transparent conductive film. The process of forming a crystalline transparent conductive film is preferably carried out under a condition of 0.02 Pa or more and 0.5 Pa or less (or 0.04 Pa or more and 0.4 Pa or less, 0.05 Pa or more and 0.3 Pa or less). As described above, for example, by adjusting the pressure in the chamber during sputtering, the crystallinity of the transparent conductive film can be adjusted.

[0047] The present invention also provides a method for manufacturing a solar cell. This method includes the steps of forming a (hole) blocking layer on the transparent electrode (transparent conductive laminate) described above, forming a perovskite layer on the (hole) blocking layer, forming an (electron) blocking layer on the perovskite layer, and forming an electrode on the (electron) blocking layer. These steps are publicly known, and solar cells can be manufactured according to the publicly known methods. EXAMPLES

[0048] In the examples, the following equipment was used: Atmospheric pressure N 2 Plasma (JP-100HA, Aqua) RF sputtering equipment (CV-19D-RDSP, Cryovac) Resistivity meter (Loresta-GX MCP-T700, Nitto Seiko) X-ray diffraction equipment (RINT 2500, Rigaku) Stylus type step meter (alpha-step IQ, KLA-Tencor) Resistance heating vacuum deposition machine (E-80LL-TransB, ALS Technology) Solar simulator (OTENTO-SUN, Spectrometer)

[0049] 1. Preparation of ITO sputtered film 1.1 Substrate preparation A 4 μm thick PEN film was used as the substrate. To make the process easier, a glass plate (0.9 mm) with an adhesive film attached was used as the support, and the PEN film was attached on top of it. The support was heat-treated at 100°C for more than 30 minutes before the PEN was attached. All subsequent treatments were performed using a glass / adhesive film / PEN system. The surface of the PEN film was washed with running ultrapure water and IPA, and then dried at 100°C for more than 30 minutes. It was then stored in a vacuum and then dried under N 2 The gas replacement was repeated to remove any air bubbles that had formed between the adhesive film and the PEN film. Just before sputtering, atmospheric pressure N was applied to the PEN film surface. 2 The plasma (power 200 W, JP-100HA, Aqua) was swept at a speed of 2.6 mm / s (a total of four times).

[0050] 1.2 ITO sputtering ITO thin films were sputtered using an RF sputtering system (CV-19D-RDSP, Cryovac). The sputtering target was 99.99% ITO (10% SnO 2 The residual gas in the chamber was 5×10 -4 The first ITO sputtering (amorphous ITO-A) was performed with Ar gas at 20 sccm and O 2 Gas was flowed at 0.06 sccm (gas pressure ratio 0.3%), the pump conductance was adjusted so that the chamber pressure was 5 Pa, the output was 50 W, and the substrate temperature was room temperature. This resulted in the deposition of an amorphous ITO-A layer with a thickness of approximately 50 nm. In order to remove contamination from the target surface, a 5-minute pre-sputtering was performed before the deposition. Note that the substrate stage was rotated during deposition to ensure the ITO film was uniform. The second ITO sputtering (crystalline ITO-C) was performed with Ar gas at 15 sccm, O2 The gas was flowed at 0.045 sccm (gas pressure ratio 0.3%), and the pump conductance was adjusted so that the chamber pressure was 0.1 Pa. The output was 50 W and the substrate temperature was 150°C. This resulted in the deposition of a crystalline ITO-C film with a thickness of approximately 150 nm.

[0051] 1.3 Measurement of ITO film properties To measure the sheet resistance of the obtained ITO film, a 0.9 mm thick glass plate was used instead of the PEN film to prepare an ITO film similar to that described in section 1.2. The electrical resistivity was measured by the four-point probe method (Loresta-GX MCP-T700, Nitto Seiko). In addition, XRD measurements were performed to confirm the crystallinity of the ITO film (RINT 2500, Rigaku). The light source was a Cu Ka (wavelength 1.54 angstroms) with an output of 12 kV.

[0052] Figure 1 is a graph instead of a drawing showing the XRD measurement results of the glass / ITO thin film. In Figure 1, each crystal peak is assigned an index. As shown in Figure 1, the XRD measurement results confirmed that the ITO-A layer formed at room temperature (RT) did not show any crystal peaks derived from ITO and was amorphous. In addition, the ITO-C layer formed at 150°C showed XRD peaks derived from ITO crystals, confirming that a crystalline ITO film had been formed. XRD peaks were also observed in the ITO-A / ITO-C two-layer laminate film, confirming that a crystalline ITO film had been formed. In addition, to measure the internal stress of the ITO film, three types of ITO films (amorphous ITO-A layer with a thickness of about 50 nm, crystalline ITO-C with a thickness of about 150 nm, and crystalline ITO-C layer with a thickness of about 150 nm formed on amorphous ITO-A layer with a thickness of about 50 nm) were fabricated using a glass plate with a thickness of 40 to 60 μm instead of the PEN film, following the same procedure as in section 1.2. The glass plate warped according to the stress of the ITO after ITO sputtering, so the displacement was measured with a stylus step gauge (alpha-step IQ, KLA-Tencor). The relationship between the displacement (radius of curvature) and the internal stress (σ) was calculated using the Stoney equation shown in the following formula (1).

[0053]

number

[0054] Here, E s is Young's modulus, t s is the thickness of the substrate, v c is the Poisson's ratio, R is the radius of curvature of the substrate, and t f The measurement results are summarized in Table 1.

[0055] [Table 1]

[0056] The first ITO-A had an amorphous ITO layer formed, and its internal stress showed a positive value. On the other hand, the second ITO-C had a crystalline ITO layer formed, and its internal stress showed a negative value. When ITO-A / ITO-C were laminated, the respective stresses were offset, resulting in an intermediate value. This result demonstrated that it was possible to reduce internal stress while maintaining a low resistivity. Next, to investigate the relationship between internal stress and the thickness of the ITO film in which the two layers were laminated, the thickness of the ITO-C layer was fixed at 150 nm, and the internal stress was measured when the thickness of the ITO-A layer was changed. The results are shown in Figure 2.

[0057] Figure 2 shows the results of measuring the internal stress when the thickness of the ITO-C layer is fixed at 150 nm and the thickness of the ITO-A layer is changed. Figure 2(a) is a graph instead of a drawing showing the relationship between internal stress and ITO-A film thickness. Figure 2(b) is a photograph instead of a drawing showing the appearance of each PEN film. In the figure, Thickness of ITO-A / ITO-C refers to the film thickness of ITO-A and ITO-C.

[0058] As shown in Fig. 2(a), the internal stress decreased as the thickness of the ITO-A layer increased, and when the thickness of the ITO-A layer was 200 nm, the internal stress decreased to 1.4% of that without the ITO-A layer. As shown in Fig. 2(b), when the ITO-A layer was not inserted, a large deformation was observed in the PEN film, but when the ITO-A layer was inserted, the deformation of the PEN film could be significantly suppressed.

[0059] Next, the transmittance of the ITO film was measured. Since the 4 μm thick PEN film had strong interference from the film itself, a 0.9 mm thick glass substrate was used as the evaluation substrate in addition to the PEN / ITO film. The glass plate was ultrasonically cleaned in ultrapure water and then in isopropanol for at least 10 minutes each, and the substrate surface was subjected to atmospheric pressure N 2 The plasma (200 W) was swept at a speed of 2.6 mm / s (a total of four times). Light was incident from the substrate side, and the total light transmittance, including diffuse light, was measured using an integrating sphere as a detector for transmitted light. Figure 3 shows the total light transmittance of a substrate with a single layer of ITO-C with a thickness of 200 nm and a substrate (PEN / two-layer ITO substrate) with a total thickness of 200 nm of ITO-A layer (50 nm) / ITO-C layer (150 nm).

[0060] Figure 3 is a graph in lieu of a drawing showing the total light transmittance of the substrate. Figure 3(a) shows the transmittance of the glass / ITO substrate, and Figure 3(b) shows the transmittance of the PEN / ITO substrate. Figure 3 confirms that in both the glass and PEN substrates, at wavelengths around 550 nm and >800 nm, the transmittance of the substrate on which two layers of ITO are formed is greater than the transmittance of the substrate on which a single layer of ITO is formed.

[0061] 2. Fabrication and evaluation of metal halide perovskite solar cells 2.1 Fabrication of metal halide perovskite solar cells Using the PEN / two-layer ITO substrate prepared by the above procedure, a perovskite solar cell was fabricated. However, to ensure that deformation due to the deposition of the ITO-C layer was prevented, the thickness of the ITO-A layer was set to 75 nm. The substrate size was 25 × 25 mm, and the ITO deposition area was 21 × 14 mm. The substrate was washed with running ultrapure water and then isopropanol, and then dried at 100 °C for 30 minutes or more. SnO 2 Just before applying the solution and the perovskite precursor solution, atmospheric pressure N 2 The plasma (200 W) was swept at a speed of 2.6 mm / s (total of four times). 2 After filtering the nanoparticle dispersion solution (15 wt%) through a PVDF filter, about 300 μL was applied to an ITO substrate and spin-coated. The rotational speed was accelerated to 2000 rpm in 1 second, maintained for 30 seconds, and then decelerated to 0.05 sec. The substrate was then baked at 140°C for 30 minutes. All of these operations were carried out in air.

[0062] Next, in a glove box (nitrogen gas atmosphere, O 2 < 0.5 ppm, H 2 A perovskite precursor solution was prepared using a 1000 ppm O solution containing CsI (44.3 mg), methylamine hydrobromide (MABr, 54.3 mg), lead(II) bromide (PbBr 2 ,121.4 mg),Lead(II) Iodide (PbI 2 ,149.5 mg),Formamidinium lead triiodide (FAPbI 3 The mixture was stirred at 40°C for 30 min to obtain Cs 0.05 FA 0.80 MA 0.15 PbI 2.65 Br 0.35A precursor solution of perovskite semiconductor with the composition was prepared. After filtering this solution through a PTFE filter, approximately 190 μL was applied to an ITO substrate and spin-coated. The perovskite film was formed using the "poor solvent method," in which a poor solvent is dropped during spin-coating to forcibly precipitate crystals. The spin-coating was accelerated to 1000 rpm in 1 second, maintained for 10 seconds, then accelerated to 3000 rpm in 5 seconds, maintained for 20 seconds, and finally stopped after deceleration of 1 second. 32 seconds after the start of spin-coating, 350 μL of super-dehydrated chlorobenzene was dropped onto the substrate surface as a poor solvent, and the substrate was immediately annealed at 160°C for 10 minutes to obtain a thin film of perovskite semiconductor. The solution for the organic semiconductor layer to be coated on the obtained perovskite crystal thin film was prepared by mixing Spiro-OMeTAD (72.3 mg), Li-TFSA (Bis(trifluoromethane) sulfonimide lithium salt) (9.1 mg), Co-3TFSI (FK209 Co(III) TFSI salt (13.5 mg), 4-tert-butylpyridine (26.6 mg), and ultra-dehydrated chlorobenzene (1 mL) and stirring at 70 °C for 30 min. After filtering the solution through a PTFE filter, about 90 μL was coated on the perovskite thin film substrate and spin-coated to form an organic semiconductor thin film. The spin-coating was accelerated to 4000 rpm in 4 s, maintained for 30 s, and then decelerated for 4 s. The obtained thin film was then annealed at 70 °C for 30 min. Finally, a 80 μL solution was vacuum-deposited as an electrode. A gold film with a thickness of 100 nm was formed. The deposition machine used was E-80LL-TransB, manufactured by ALS Technology. The gold electrode was a rectangle of 0.3 × 1.6 cm, and the effective area of ​​the solar cell was 0.1 cm. 2 It was decided.

[0063] Figure 4 is a photograph of the obtained solar cell in place of a drawing. Figure 4(a) shows the cross-sectional structure of the solar cell, and Figure 4(b) shows a photograph of the solar cell. For comparison, a solar cell was fabricated in which only ITO-C was deposited, but it was significantly deformed and failed due to a short circuit. On the other hand, when two layers of ITO were used, a relatively flat solar cell was obtained. In Figure 4, Spiro-OMeTAD stands for [2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamino)-9,9'-spirobifluorene] (electron blocking layer), and Perovskite stands for the perovskite layer.

[0064] 2.2 Measurement of metal halide perovskite solar cells Perovskite solar cells fabricated on a 4 μm thick PEN film under simulated solar light irradiation (OTENTO-SUN, Spectrometer, light source intensity 100 mW / cm -2 The photoelectric conversion efficiency was measured in a glove box (nitrogen gas atmosphere, O 2 < 0.5 ppm, H 2 The measurements were performed at a concentration of 0.05 ppm and the results are shown in Figure 5.

[0065] FIG. 5 is a graph in lieu of a drawing showing the results of measuring the characteristics of the solar cell obtained in the embodiment. FIG. 5(a) shows the current-voltage characteristics of the solar cell, and FIG. 5(b) shows the spectral sensitivity characteristics of the solar cell. As shown in FIG. 5, the current density J sc = 21.9 mA / cm 2 , release voltage V oc = 1.04 V, fill factor FF = 0.68, and conversion efficiency η = 15.4%. The spectral sensitivity characteristics almost reflected the transmittance in Figure 3. In Figure 5, Current density indicates the current density, Forward indicates the forward direction, Reverse indicates the reverse direction, Voltage indicates the voltage, and Wavelength indicates the wavelength.

[0066] 3. Discussion As shown by the examples, it was shown that forming amorphous ITO / crystalline ITO can adequately prevent warping of the substrate. This shows that this invention is effective for film-type transparent conductive laminates and transparent electrodes. Such transparent conductive laminates are used in elements such as solar cells and organic EL devices. In the above examples, a film-type perovskite solar cell was actually fabricated and its effectiveness was demonstrated. This invention is not limited to the above examples. Even if various conditions are changed in these examples, it is believed that it is possible to prevent warping of the substrate and obtain an effective element as long as it is included in the concept of this invention. [Industrial Applicability]

[0067] This invention can be used in fields such as solar cells and organic electroluminescence (EL).

Claims

1. A resin substrate; An amorphous transparent conductive film provided on the resin substrate; a crystalline transparent conductive film provided on the amorphous transparent conductive film; a light absorbing layer including a compound having a perovskite structure provided on the crystalline transparent conductive film; A solar cell comprising: The thickness of the crystalline transparent conductive film is d Ｃ Then, d Ｃ is 80 nm or more and 300 nm or less, The thickness of the amorphous transparent conductive film is d Ａ Then, d Ａ / d Ｃ is between 1 / 3 and 4 / 5, Solar cell.

2. The solar cell according to claim 1 , The thickness of the resin substrate is 0.1 μm or more and 100 μm or less. Solar cell.

3. The solar cell according to claim 1 , The thickness of the resin substrate is 1 μm or more and 10 μm or less. Solar cell.

4. The solar cell according to claim 1 , the crystalline transparent conductive film and the non-crystalline transparent conductive film are ITO films; Solar cell.

5. The solar cell according to claim 1 , The internal stress of the amorphous transparent conductive film is positive, The internal stress of the crystalline transparent conductive film is negative. Solar cell.

6. A method for manufacturing a solar cell, comprising: A step of forming an amorphous transparent conductive film having a positive internal stress on a resin substrate; forming a crystalline transparent conductive film having a negative internal stress on the amorphous transparent conductive film after forming the amorphous transparent conductive film; After forming the crystalline transparent conductive film, a step of forming a light absorbing layer containing a compound having a perovskite structure on the crystalline transparent conductive film is included, The thickness of the crystalline transparent conductive film is d Ｃ Then, d Ｃ is 80 nm or more and 300 nm or less, The thickness of the amorphous transparent conductive film is d Ａ Then, d Ａ / d Ｃ is greater than or equal to 1 / 3 and less than or equal to 4 / 5.

7. The method for producing a solar cell according to claim 6, comprising the steps of: The step of forming the amorphous transparent conductive film is carried out under a condition of 1 Pa or more and 20 Pa or less, The step of forming the crystalline transparent conductive film is carried out under a condition of 0.02 Pa or more and 0.5 Pa or less.

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