Photoelectric conversion element and manufacturing method of the same

Abstract

To provide a photoelectric conversion element low in possibility of occurrence of short circuit and leakage.SOLUTION: A photoelectric conversion element 1 includes: a light absorption layer 13 that receives light and causes charge separation between a positive hole and an electron; and a transport layer 14 that is formed on the light absorption layer 13 and includes a transport material for transporting the positive hole and an electron. In the photoelectric conversion element 1, the surface of the light absorption layer 13 is modified with a poor solvent that does not dissolve the light absorption layer 13, and the transport layer 14 is formed on the modified surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion element and a method for manufacturing the same. [Background technology]

[0002] A technique for reducing short circuits and leakage and improving yield in photoelectric conversion elements that use crystals with a perovskite structure in the light absorption layer is known (see, for example, Patent Document 1). The photoelectric conversion element described in Patent Document 1 has a first transport layer (buffer layer) formed by a wet process and a second transport layer formed by a dry process disposed between the light absorption layer (active layer) and the electrode. This makes it possible to fabricate photoelectric conversion elements that reduce short circuits and leakage and improve yield. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2021-77788 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technique described in Patent Document 1 leaves surface defects on the light absorption layer, which may result in a decrease in power generation efficiency.

[0005] The present invention is intended to solve such problems, and provides a photoelectric conversion element in which surface defects in the light absorption layer are reduced. [Means for solving the problem]

[0006] The photoelectric conversion element according to the present invention is a photoelectric conversion element having a light absorbing layer that receives light and causes charge separation of holes and electrons, and a transport layer formed on the light absorbing layer and containing a transport material for transporting holes or electrons, wherein the surface of the light absorbing layer is modified with a poor solvent that does not dissolve the light absorbing layer, and the transport layer is formed on the modified surface.

[0007] Furthermore, in the photoelectric conversion element according to the present invention, the transport layer preferably includes a layer formed by a wet process using a solution containing a solvent that modifies surface defects of the light absorption layer.

[0008] Furthermore, in the photoelectric conversion element according to the present invention, it is preferable that the transport layer has a first layer formed on the light absorbing layer and a second layer formed on the first layer, the first layer being a layer formed by a wet process and including an opening region that does not cover the light absorbing layer, and the second layer being in contact with the first layer and the light absorbing layer via the opening region.

[0009] Furthermore, in the photoelectric conversion element according to the present invention, the second layer preferably contains the same transport material as the transport material contained in the first layer.

[0010] Furthermore, in the photoelectric conversion element according to the present invention, the first layer is a compound containing fullerene and phenyl-C 61 Preferably, the first layer contains methyl butyl ester, and the second layer contains fullerene.

[0011] Furthermore, in the photoelectric conversion element according to the present invention, the hysteresis index, which is the absolute value of the difference between the energy conversion efficiency of forward scanning obtained by scanning the applied voltage in the positive direction and the energy conversion efficiency of reverse scanning obtained by scanning the applied voltage in the negative direction, divided by the energy conversion efficiency of reverse scanning, is preferably 7.7% or less.

[0012] Furthermore, the method for manufacturing a photoelectric conversion element according to the present invention includes the steps of forming a light absorbing layer that receives light and causes charge separation of holes and electrons, and forming a hole or electron transport layer on the light absorbing layer, and further includes a process of modifying the surface of the light absorbing layer with a poor solvent that does not dissolve the light absorbing layer, and forming the transport layer on the modified surface. [Effects of the Invention]

[0013] The photoelectric conversion element according to the present invention can reduce defects at the interface between the light absorption layer and the buffer layer. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a plan view of a photoelectric conversion element according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA′ shown in FIG. [Figure 3] 2A to 2C are diagrams showing a method for manufacturing the photoelectric conversion element shown in FIG. 1, in which (a) shows a lower conductive layer forming step, (b) shows a hole transport layer forming step, (c) shows a light absorbing layer forming step, (d) shows a first layer forming step, (e) shows a second layer forming step, (f) shows a forming layer removing step, and (g) shows an electrode forming step. [Figure 4] (a) is a schematic diagram of the light-absorbing layer before the electron transport layer is disposed, (b) is a schematic diagram of the light-absorbing layer whose surface has been modified with a solution, and (c) is a schematic diagram of the light-absorbing layer on which the first and second layers have been deposited. [Figure 5] FIG. 4 is a cross-sectional view of a photoelectric conversion element according to a second embodiment. [Figure 6] FIG. 1 is a graph showing the change over time in PCE in Examples 1 to 4 and Comparative Example 1. [Figure 7] FIG. 1(a) is a graph showing the current-voltage characteristics of a photoelectric conversion element according to Example 5 under light irradiation, and FIG. 1(b) is a graph showing the current-voltage characteristics of a photoelectric conversion element according to Comparative Example 2 under light irradiation. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a photoelectric conversion element and a method for manufacturing the same according to the present invention will now be described with reference to the drawings.

[0016] (Photoelectric conversion element according to an embodiment) 1 and 2 are diagrams showing the configuration of a photoelectric conversion element according to an embodiment.

[0017] The photoelectric conversion element 1 has a substrate 10, a lower conductive layer 11, a hole transport layer 12, a light absorbing layer 13, an electron transport layer 14, a lower electrode 15, and an upper electrode 16. The photoelectric conversion element 1 is an element in which light is incident on the light absorbing layer 13 through the lower conductive layer 11 and the hole transport layer 12, generating a voltage between the lower electrode 15 and the upper electrode 16, and converting light energy into electrical energy so that a current is output from the lower electrode 15.

[0018] The substrate 10 is capable of supporting the components included in the photoelectric conversion element 1 and is made of a light-transmitting material that transmits light of a wavelength that is absorbed by the light absorption layer 13. The substrate 10 is formed from a glass substrate or a flexible synthetic resin.

[0019] The lower conductive layer 11 is made of a light-transmitting, low-resistance material capable of transporting holes and is deposited to cover the substrate 10. The lower conductive layer 11 may be made of, for example, tin-doped indium oxide (ITO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), or niobium-doped titanium oxide (NTO).

[0020] The hole transport layer 12 is a p-type semiconductor transport layer that transports holes generated in the light absorption layer 13 to the lower conductive layer 11, and is formed on the lower conductive layer 11. The hole transport layer 12 is light-transmitting and is made of, for example, nickel oxide (NiO x ), cuprous oxide (Cu2O), molybdenum oxide (MoO3), and other oxides.

[0021] The light absorbing layer 13 is formed on the hole transport layer 12, absorbs light incident through the lower conductive layer 11 and the hole transport layer 12, and is excited to generate electrons and holes inside. The holes generated inside the light absorbing layer 13 are transported to the lower electrode 15 via the hole transport layer 12 and the lower conductive layer 11, and the electrons generated inside the light absorbing layer 13 are transported to the upper electrode 16 via the electron transport layer 14. The light absorbing layer 13 may be, for example, a layer having a composition formula of Ag a Bi b I c It is formed by Rudolf Phyte material shown by Ag a Bi b I c In the formula, a, b, and c represent the composition ratio.

[0022] The electron transport layer 14, also referred to as a buffer layer, is an n-type semiconductor transport layer that transports electrons generated in the light absorption layer 13 to the upper electrode 16, and is formed on the light absorption layer 13. In the present embodiment, the electron transport layer 14 is formed by depositing a first layer 141 and a second layer 142 in this order from the light absorption layer 13 side.

[0023] The first layer 141 is formed by a wet process using a solution containing a solvent that modifies surface defects of the light absorbing layer 13. This solvent is a good solvent for the material that forms the electron transport layer 14, but a poor solvent for the material that forms the light absorbing layer 13. For example, if the light absorbing layer 13 is formed of a compound having the composition formula Ag a Bi b I c When using fullerene (C 60 ), phenyl-C 61 The first layer 141 is disposed on the surface of the light absorbing layer 13 so as to cover the upper surface of the light absorbing layer 13. The first layer 141 is a polyisocyanate (PCBM) and ITIC, and the solvent can be chlorobenzene or toluene.

[0024] The solvent that modifies the surface defects of the light absorbing layer 13 is a poor solvent for the material forming the light absorbing layer 13, but it exhibits reactivity that improves the defects in the bonds between atoms that occur on the surface of the light absorbing layer 13, and a surface-modified layer is formed on the surface of the light absorbing layer 13 on the side where the transport layer 14 is formed. This reduces trap levels caused by interfacial defects between the light absorbing layer 13 and the first layer 141. Note that the surface-modified layer formed at the interface between the light absorbing layer 13 and the first layer 141 has a thickness of 1 nm or less, and therefore it is not easy to confirm the state of modification even when observing the cross section of the photoelectric conversion element 1 using a high-sensitivity microscope such as a scanning electron microscope (SEM).

[0025] The second layer 142 is formed by a dry process so as to cover the upper surface of the first layer 141. The second layer 142 is made of, for example, C 60 When the first transport layer has one or more open regions, the second layer 142 is formed so as to be in contact with the light absorbing layer 13 via the open region.

[0026] The electron transport layer 14 preferably has a thickness of 1 nm to 60 nm, more preferably 2 nm to 30 nm. If the thickness of the electron transport layer 14 is thinner than 1 nm, the light absorption layer 13 may not be sufficiently covered by the electron transport layer 14. If the thickness of the electron transport layer 14 is thicker than 60 nm, the resistance between the upper electrode 16 and the light absorption layer 13 increases, and the conversion efficiency of the photoelectric conversion element 1 decreases.

[0027] The lower electrode 15 is formed on the lower conductive layer 11, and the upper electrode 16 is formed on the electron transport layer 14. The lower electrode 15 and the upper electrode 16 are formed of materials that are in ohmic contact with the lower conductive layer 11 and the electron transport layer 14, and are formed as a single layer of a metal such as Bi, Ti, Ag, Al, Zn, Au, or Pt, or a carbon-based electrode such as graphite, or as a multiple laminate of two or more types, such as Ti / Au.

[0028] (Method of manufacturing a photoelectric conversion element) Next, a method for manufacturing the photoelectric conversion element 1 will be described with reference to FIG.

[0029] 3(a), in the lower conductive layer formation step, a lower conductive layer 11 is formed on a substrate 10 having a rectangular planar shape. The lower conductive layer 11 is formed by a film formation method such as a vacuum deposition method, a sputtering method, a CVD method, or a plating method.

[0030] 3(b), a hole transport layer 12 is patterned on the surface of the lower conductive layer 11. The hole transport layer 12 is formed by a film formation method such as vacuum deposition, sputtering, CVD, or plating. The patterned film formation can be achieved by mask deposition or photolithography.

[0031] Next, in the light absorbing layer forming step shown in FIG. 3(c), the light absorbing layer 13 is formed. The light absorbing layer 13 is formed by, for example, spin coating so as to cover the lower conductive layer 11 and the hole transport layer 12. In the light absorbing layer forming step, first, a precursor-containing solution containing a precursor material for the light absorbing layer 13 and an organic solvent is applied by spin coating to the hole transport layer 12 formed in the hole transport layer forming step. Next, the substrate 10 on which the precursor-containing solution has been applied is heated to dry and bake, thereby volatilizing the solvent and forming the light absorbing layer 13. Here, the crystalline structure of the light absorbing layer 13 is formed by a wet process that volatilizes the solvent, but surface defects are likely to occur on the outermost surface of the light absorbing layer 13 during the drying and baking steps.

[0032] Next, in the first layer deposition step shown in FIG. 3(d), a first layer 141, which is an electron transport layer, is deposited by a wet process. The first layer 141 is deposited by, for example, spin coating so as to cover the light absorbing layer 13. In the first layer deposition step, a transport layer solution containing an electron transport material and an organic solvent is first applied to the light absorbing layer 13 by spin coating, followed by drying or pre-drying and baking to volatilize the solvent, thereby depositing the first layer 141. As described above, the organic solvent used in this step is a good solvent for the electron transport material and a poor solvent for the light absorbing layer 13, which has the reactivity to modify the surface layer. Therefore, when the transport layer solution is applied to the surface of the light absorbing layer 13, a surface-modified layer is formed on the surface of the light absorbing layer 13.

[0033] 3(e), a second layer 142 is formed by a dry process on the surface of the lower conductive layer 11. The second layer 142 is formed by, for example, vacuum deposition.

[0034] 3(f), the formed light absorbing layer 13 and the electron transport layer 14 (the first layer 141 and the second layer 142) are removed except for the regions corresponding to the hole transport layer 12. The removal process can be achieved by placing a metal mask and removing the exposed light absorbing layer 13 and the electron transport layer 14 with a solvent. This exposes a portion of the lower conductive layer 11.

[0035] 3(g), a lower electrode 15 and an upper electrode 16 are formed on the surface of the lower conductive layer 11 and the surface of the electron transport layer 14. The lower electrode 15 and the upper electrode 16 are formed in a pattern by, for example, vacuum deposition. The pattern formation is similar to that for the hole transport layer 12 described above. Through the above steps, the photoelectric conversion element 1 is manufactured.

[0036] Since the second layer 142 is formed by a dry process on the first layer 141 formed by a wet process, it is possible to prevent the light absorption layer 13 from being altered by the influence of heat in the film formation process.

[0037] The surface modification between the light absorbing layer 13 and the electron transport layer 14 will be described with reference to FIGS. 4(a) and 4(b).

[0038] 4(a), before the electron transport layer 14 is formed, the surface of the light absorbing layer 13 has uneven regions 130 including flat portions, recessed portions, protrusions, and inclined portions, and also has surface defects 131. When the first layer 141 is formed by a wet process using a solvent that is a poor solvent for the material that forms the light absorbing layer 13, the solvent inactivates the surface defects 131 of the light absorbing layer 13, and the surface of the light absorbing layer 13 becomes a modified light absorbing layer (surface modified layer) 132 (see FIG. 4(b)).

[0039] By improving defects at the interface between the light absorption layer 13 and the electron transport layer 14, it is possible to reduce variations between elements when fabricating multiple photoelectric conversion elements on the same substrate. Furthermore, the photoelectric conversion element 1 can have a smaller hysteresis index by reducing the trap level. The hysteresis index Hi can be calculated from the power conversion efficiency (PCE) as shown in the following formula (1), and is the PCE for forward scanning obtained by scanning the applied voltage in the forward direction. forward and PCE, which is the PCE of the reverse scan obtained by scanning the applied voltage in the negative direction. reverse The absolute value of the difference between reverse It can be calculated by dividing by .

[0040]

number

[0041] The hysteresis index is preferably 15.0% or less, more preferably 10.0% or less, and even more preferably 7.7% or less.

[0042] Furthermore, when the first layer 141 is formed by a wet process, it may include an opening region 133 where the light absorbing layer 13 is not covered and a region 134 on a protrusion where the transport layer solution is difficult to apply. As shown in FIG. 4( c), by forming the second layer 142 on the first layer 141 by a dry process, the opening region 133 and the region 134 where the transport layer solution is difficult to apply are covered, thereby improving the coverage of the transport layer 14 on the light absorbing layer 13. Because the surface of the first layer 141 is formed by a wet process, it has improved flatness compared to the surface of the light absorbing layer 13. In the photoelectric conversion element 1, the second layer 142 can cover the opening region 133 and the region 134 where the transport layer solution is difficult to apply, which are included in the first layer 141, and therefore, the photoelectric conversion element 1 can further reduce short circuits and leaks that occur when the upper electrode 16 and the light absorbing layer 13 contact each other. Furthermore, in the photoelectric conversion element 1, the second layer 142 can cover the opening region 133 included in the first layer 141 and the region 134 where the transport layer solution is difficult to apply, thereby preventing mutual diffusion of the materials forming the light absorption layer 13 and the upper electrode 16.

[0043] In the photoelectric conversion element 1, the second layer 142 contains the same transport material as the transport material contained in the first layer 141, C 60 Since the first layer 141 and the second layer 142 contain the compound, they have high adhesion to each other, and the decrease in PCE caused by laminating the second layer 142 is suppressed.

[0044] In addition, the first layer 141 of the photoelectric conversion element 1 is C 60 and PCBM, and the second layer 142 is formed of C 60 Therefore, there is little risk of defects occurring at the interface between the first layer 141 and the second layer 142, and a high PCE can be achieved.

[0045] (Photoelectric conversion element according to the second embodiment) 5 is a cross-sectional view of a photoelectric conversion element according to the second embodiment, which corresponds to the cross-sectional view taken along line AA' in FIG.

[0046] The photoelectric conversion element 2 differs from the photoelectric conversion element 1 in that it has an electron transport layer 24 instead of the electron transport layer 14. The configurations and functions of the components of the photoelectric conversion element 2 other than the electron transport layer 24 are the same as the configurations and functions of the components of the photoelectric conversion element 1 that are assigned the same reference numerals, and therefore detailed explanations thereof will be omitted.

[0047] The electron transport layer 24 is made of C, similar to the first layer 141. 60 and PCBM, and is deposited by a wet process using a solution containing a solvent that modifies surface defects in the light-absorbing layer. The electron transport layer 24 is disposed so as to cover the upper surface of the light-absorbing layer 13. The electron transport layer 24 preferably has a thickness of 1 nm or more and 60 nm or less, and more preferably has a thickness of 2 nm or more and 30 nm or less. If the thickness of the electron transport layer 24 is thinner than 1 nm, the light-absorbing layer 13 may not be sufficiently covered by the electron transport layer 14. If the thickness of the electron transport layer 24 is thicker than 60 nm, the resistance between the upper electrode 16 and the light-absorbing layer 13 increases, and the conversion efficiency of the photoelectric conversion element 1 decreases.

[0048] The method for manufacturing the photoelectric conversion element 2 is the same as the method for manufacturing the photoelectric conversion element 1 except that the electron transport layer 24 is formed in the same manner as the method for forming the first layer 141, and therefore a description thereof will be omitted.

[0049] (Photoelectric Conversion Element According to Modification) Although the photoelectric conversion elements 1 and 2 are inverted-structure photoelectric conversion elements, they may also be forward-structure photoelectric conversion elements in which a light-absorbing layer is formed on an electron-transporting layer and a hole-transporting layer is formed on the light-absorbing layer. When the photoelectric conversion element according to the embodiment is a forward-structure photoelectric conversion element, the hole-transporting layer is formed to include a layer formed by a wet process. The organic solvent used to form the hole-transporting layer is a good solvent for the hole-transporting material but a poor solvent for the light-absorbing layer 13, which is reactive enough to modify the surface layer. The hole-transporting layer is formed by a wet process using a solution containing an organic solvent that is a good solvent for the hole-transporting material but a poor solvent for the light-absorbing layer 13, which is reactive enough to modify the surface layer. Furthermore, similar to the photoelectric conversion element 1, a first layer may be formed by a wet process, and a second layer may be formed on the first layer.

[0050] Furthermore, in the photoelectric conversion element according to the embodiment, the surface of the light absorbing layer 13 may be modified with a poor solvent that does not dissolve the light absorbing layer 13, and the electron transport layer may be formed on the surface of the modified light absorbing layer 13. The electron transport layer formed on the surface of the modified light absorbing layer 13 may be formed by a dry process or a wet process.

[0051] In the photoelectric conversion element according to the embodiment, the first layer is made of C 60 and PCBM.

[0052] In the photoelectric conversion element according to the embodiment, the second layer 142 may not contain the transport material contained in the first layer 141. For example, when the first layer 141 is formed of PCBM, the second layer 142 may contain C 60 It may be formed by:

[0053] In the photoelectric conversion element according to the embodiment, the second layer may be formed by a wet process.

[0054] In the photoelectric conversion element according to the embodiment, the electron transport layer formed by the wet process is C 60and PCBM. [Example]

[0055] Photoelectric conversion elements according to Examples and Comparative Examples were fabricated, and the power generation characteristics obtained by performing current-voltage measurements on the fabricated photoelectric conversion elements will be described below.

[0056] (Method for measuring current-voltage characteristics under light irradiation) The current-voltage characteristics under light irradiation were measured using the following method. A BLD-100 light source manufactured by Bunkoukeiki Co., Ltd. was used, and the illuminance was adjusted so that the incident light from the light source onto the photoelectric conversion element was 200 lx. The light emitted from the light source was adjusted to be emitted over an area of 2.5 mm x 2.5 mm using a light-shielding mask, and the light source and photoelectric conversion element were positioned so that the light was incident on the photoelectric conversion element from the substrate side. The current-voltage characteristics were measured using a PECK2400-N manufactured by Peccell Technologies Co., Ltd., by sequentially scanning the voltage applied to the photoelectric conversion element from positive to negative.

[0057] Example 1 Example 1 was produced by the manufacturing method shown in Figure 3. First, an ITO glass substrate having a planar shape of 25 mm x 25 mm and having a lower conductive layer 11 formed on a substrate 10 was prepared, and the prepared ITO glass substrate was subjected to UV ozone cleaning. Here, the thickness of the glass substrate corresponding to the substrate 10 was 0.7 mm, and the thickness of the ITO film corresponding to the lower conductive layer 11 was 0.15 µm.

[0058] Next, a NiO:Zn layer corresponding to the hole transport layer 12 was formed on the surface of the ITO film formed on the ITO glass substrate by vacuum deposition using an EX-200 manufactured by ULVAC, Inc., and heating with an EB gun.

[0059] Next, Ag2Bi corresponding to the light absorption layer 13 4.5 I 15.5The film was formed by spin-coating a solution containing a Rudolphite material precursor, which was prepared by dissolving AgI and BiI3 in DMSO as a solvent, onto the surface of the hole transport layer 12. The Rudolphite material precursor solution was prepared so that the ratio of Ag:Bi:I in the Rudolphite material precursor solution was 2:4.5:15.5. The Ag2Bi corresponding to the light absorption layer 13 4.5 I 15.5 The film thickness was 400 nm.

[0060] Next, a layer corresponding to the first layer 141 was deposited on the surface of the light absorbing layer 13. The material used to deposit the first layer 141 was C as a transport material. 60 and PCBM in the transport layer solution using chlorobenzene as the solvent. 60 and PCBM at a ratio of 1:1. The thickness of the layer corresponding to the deposited first layer 141 was 20 nm.

[0061] Next, a layer corresponding to the second layer 142 was formed on the surface of the first layer 141. The material of the second layer 142, C, was heated by a resistance heating source by a vacuum deposition method using an EX-200 manufactured by ULVAC, Inc. 60 The powder is heated to C 60 was evaporated to form a film on the surface of the first layer 141. The film thickness of the formed layer was 4 nm.

[0062] Next, the region where the electron transport layer 14 is formed is limited by a metal mask, and the portions of the hole transport layer 12, the light absorption layer 13, and the electron transport layer 14 exposed from the mask are removed with DMF.

[0063] The BCP / Bi / Cr / Au layers corresponding to the lower electrode 15 and the upper electrode 16 were formed by vacuum deposition using an EX-200 manufactured by ULVAC, Inc., and heated with an EB gun. 60 The layer was deposited on the surface of the layer.

[0064] (Examples 2, 3, and 4 and Comparative Example 1) Examples 2, 3, and 4 and Comparative Example 1 differ in the layer corresponding to the electron transport layer 14. In Example 2, the transport material of the first layer 141 is C 60 In Example 3, the transport material of the first layer 141 is formed only with PCBM. In Example 4, the first layer 141 has the same configuration as the first layer 141 of Example 1, but the second layer 142 is not formed and the electron transport layer 14 is formed only with the first layer 141. In Comparative Example 1, the first layer 141 was not formed by a wet process to modify the surface of the light absorbing layer 13, and only a layer corresponding to the second layer 142 formed by a dry process was formed. In Examples 2 and 3, the thickness of the layer corresponding to the first layer 141 was 20 nm, and the thickness of the layer corresponding to the second layer 142 was 4 nm. In Example 4, the thickness of the layer corresponding to the electron transport layer 24 was 20 nm. In Comparative Example 1, the thickness of the layer corresponding to the second layer 142 was 20 nm. Since Examples 2, 3, and 4 and Comparative Example 1 have the same configuration as Example 1 except for the layer corresponding to the electron transport layer 14, detailed description thereof will be omitted here.

[0065] Each of Examples 1 to 4 and Comparative Example 1 includes 10 samples manufactured using the same manufacturing method. The PCE of each of the 10 samples in Examples 1 to 4 and Comparative Example 1 was measured 2, 6, 13, and 15 days after manufacturing, and the standard deviation of the measured PCE was calculated. When the standard deviation of the measured PCE was less than 1.0, manufacturing variation was small and the evaluation was "Good." When the standard deviation of the measured PCE was 1.0 or more, manufacturing variation was large and the evaluation was "Poor." Furthermore, when the PCE measured for all 10 samples 15 days after manufacturing was 5.0 or more, the energy conversion efficiency was high and the evaluation was "Good." When the measured PCE was all 1.0 or more but less than 5.0, power was generated but the energy conversion efficiency was relatively low and the evaluation was "Good." When the measured PCE was less than 1.0 and there was a sample that barely generated power, manufacturing variation was large and there was a risk of power generation failure, so the evaluation was "Poor."

[0066] Table 1 shows the evaluation results of Examples 1 to 4 and Comparative Example 1. The PCE shown in Table 1 and Fig. 6 indicates the PCE of the IV curve obtained by averaging the IV curve obtained by scanning the applied voltage in the positive direction and the IV curve obtained by scanning the applied voltage in the negative direction.

[0067] [Table 1]

[0068] As shown in Figure 6, in Examples 1, 2, and 3, all samples had a PCE in the range of 4% to 10%, and the standard deviations σ were very low at 0.4, 0.3, and 0.4, respectively, indicating small manufacturing variations and high PCE. In Example 4, the standard deviation σ was less than 0.8, indicating small manufacturing variations.

[0069] In Comparative Example 1, the PCE was in the range of 0% to 7%, two samples had PCEs of less than 2%, and one sample had a large change in PCE over time, resulting in a large standard deviation σ of 1.9 or more.

[0070] In Comparative Example 1, in which the surface of the light absorbing layer was not modified, the standard deviation σ was 1.0 or more, indicating large manufacturing variations and the possibility of a decrease in yield and an increase in manufacturing costs when mass-produced for commercialization. On the other hand, in Examples 1 to 4, in which the surface of the light absorbing layer was modified, the standard deviation σ was less than 1.0, indicating small manufacturing variations and a low possibility of a decrease in yield when mass-produced for commercialization, and indicating that manufacturing costs can be suppressed.

[0071] (Example 5 and Comparative Example 2) In Example 5, surface defects of the light absorbing layer 13 were modified using a poor solvent for the light absorbing layer 13, and a layer corresponding to the electron transport layer 14 was formed on the surface thereof by omitting the layer corresponding to the first layer 141 formed by a wet process and only forming a layer corresponding to the second layer 142 formed by a dry process. In Comparative Example 2, surface defects of the light absorbing layer 13 were not modified using a poor solvent for the light absorbing layer 13, and the layer corresponding to the first layer 141 formed by a wet process was omitted, forming only a layer corresponding to the second layer 142 formed by a dry process. In Example 5 and Comparative Example 2, the layer corresponding to the second layer 142 had a thickness of 4 nm. Since Example 5 and Comparative Example 2 have the same configuration as Example 1 except for the layer corresponding to the electron transport layer 14, detailed description thereof will be omitted here.

[0072] The hysteresis index was calculated for each of Example 5 and Comparative Example 2. When the calculated hysteresis index was less than 10%, the positive scan output PCE forward and reverse scan output PCE reverse The difference between the two is small, and it is considered that the trap level is decreasing, so the evaluation is "Good." When the calculated hysteresis index is 10% or more, the positive scan output PCE forward and reverse scan output PCE reverse The difference between the two is large, and it is thought that the trap level has not decreased, so the evaluation was made "X".

[0073] Table 2 shows the evaluation results of Example 5 and Comparative Example 2.

[0074] [Table 2]

[0075] 7(a) and 7(b) show the current-voltage characteristics of the photoelectric conversion elements according to Example 5 and Comparative Example 2 under light irradiation. In FIGS. 7(a) and 7(b), the horizontal axis represents the voltage generated between the lower electrode 15 and the upper electrode 16 when irradiated with light, and the vertical axis represents the current flowing from the lower electrode 15 when irradiated with light. In FIG. 7(a), L101 represents the current-voltage characteristics when the applied voltage is scanned in the positive direction, L102 represents the current-voltage characteristics when the applied voltage is scanned in the negative direction, and L103 represents the average value when the applied voltage is scanned in the positive and negative directions. In FIG. 7(b), L201 represents the current-voltage characteristics when the applied voltage is scanned in the positive direction, L202 represents the current-voltage characteristics when the applied voltage is scanned in the negative direction, and L203 represents the average value when the applied voltage is scanned in the positive and negative directions.

[0076] In Example 5, the hysteresis index was 7.7%, which was less than 10%, and the evaluation was "Good." In Example 5, the hysteresis index was small, which indicates that the trap level was reduced by forming a surface modification layer at the interface between the light absorbing layer 13 and the electron transport layer 14.

[0077] In Comparative Example 2, the hysteresis index was 26.1%, which was significantly greater than 10%, and the evaluation was given as "X." In Comparative Example 2, the hysteresis index was large, which indicates that a surface modification layer was not formed at the interface between the light absorbing layer 13 and the electron transport layer 14, and that many trap levels existed. [Explanation of symbols]

[0078] 1, 2 Photoelectric conversion element 10 Substrate 11 Lower conductive layer 12 Hole transport layer 13 Light absorption layer 14, 24 Electron transport layer (transport layer) 15 Lower electrode 16 Upper electrode 141 1st layer 142 2nd layer

Claims

1. A photoelectric conversion element having a light absorbing layer that receives light and causes charge separation of holes and electrons, and a transport layer formed on the light absorbing layer and containing a transport material for transporting holes or electrons, the surface of the light absorbing layer is modified with a poor solvent that does not dissolve the light absorbing layer; the transport layer is deposited on the modified surface; A photoelectric conversion element characterized by:

2. The photoelectric conversion element according to claim 1 , wherein the transport layer includes a layer formed by a wet process using a solution containing a solvent that modifies surface defects of the light absorption layer.

3. the transport layer has a first layer formed on the light absorbing layer and a second layer formed on the first layer; the first layer is a layer formed by a wet process using a solution containing a solvent that modifies surface defects of the light absorbing layer, and includes an open region that does not cover the light absorbing layer; the second layer is in contact with the first layer and the light absorbing layer through the opening region; The photoelectric conversion element according to claim 2 .

4. The second layer contains the same transport material as the transport material contained in the first layer. The photoelectric conversion element according to claim 3 .

5. The first layer is composed of fullerene and phenyl-C 61 - containing butyric acid methyl ester, the second layer contains fullerene; The photoelectric conversion element according to claim 4 .

6. a hysteresis index, which is a value obtained by dividing the absolute value of the difference between the energy conversion efficiency of forward scanning obtained by scanning the applied voltage in the positive direction and the energy conversion efficiency of reverse scanning obtained by scanning the applied voltage in the negative direction by the energy conversion efficiency of reverse scanning, is 7.7% or less; The photoelectric conversion element according to any one of claims 1 to 5.

7. A method for manufacturing a photoelectric conversion element, comprising the steps of forming a light absorbing layer that receives light and causes charge separation of holes and electrons, and forming a hole or electron transport layer on the light absorbing layer, modifying the surface of the light absorbing layer with a poor solvent that does not dissolve the light absorbing layer; depositing the transport layer onto the modified surface; 10. A method for producing a photoelectric conversion element, comprising the steps of:

Images