JP6764187B2 - Photoelectric conversion element and manufacturing method of photoelectric conversion element - Google Patents

Description

The present invention relates to a technique for a photoelectric conversion element capable of converting light energy into electrical energy.

In recent years, global energy demand has been increasing along with the rapid economic development of emerging countries. As a result, fossil energy costs such as petroleum are rising. In addition, the increase in fossil energy consumption in these emerging countries has led to an increase in CO ₂ emissions on a global scale, causing serious environmental destruction. Active use of natural energy has been called for as a promising candidate for solving these problems, and expectations for solar power generation using solar cells are extremely high.

Various materials are used for the solar cell, and the main ones include single crystal silicon, polycrystalline silicon, amorphous silicon, copper indium gallium selenium compound (CIGS compound) and the like. Although silicon has abundant crustal reserves, it is hard to say that it is an inexpensive material in the case of high-purity silicon, which is a raw material for solar cells. In addition, CIGS compounds contain rare metals that are difficult to obtain due to their small reserves, and there is a limit to the reduction of material costs.

Therefore, solar cells such as zinc oxide and cuprous oxide using zinc and copper whose main raw materials are extremely inexpensive and whose crustal reserves are abundant are being developed.

For example, much research has been done on the technique for producing a cuprous oxide (Cu ₂ O) layer for a solar cell. However, the only method for producing a high-quality Cu ₂ O layer is by thermal oxidation at a high temperature of about 1000 ° C. There is also a report that the Cu ₂ O layer was prepared at a relatively low temperature by the liquid phase method using an aqueous solution, but the quality is higher than that of the Cu ₂ O layer prepared by the thermal oxidation method at a high temperature. It was inferior.

In such a situation, in order to realize a "bending Cu ₂ O solar cell" on a flexible substrate such as plastic as a power source for wearable computing devices in the future, high quality Cu ₂ O at a low temperature is required. It is essential to establish a technique for producing layers. Prior to the technique for producing a high quality Cu ₂ O layer at a low temperature, the inventors of the present application have added a low resistivity to which sodium can be used as an epitaxial growth substrate indispensable for producing a high quality Cu ₂ O layer. A Cu ₂ O sheet of resistivity has already been devised (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2015-162650

As described above, although solar cells made of inexpensive materials are being realized, practically, high-quality film formation at low temperatures and further improvement of conversion efficiency are required. In order to further improve the conversion efficiency, for example, it is a good idea to manufacture a solar cell homozygous for cuprous oxide. However, although various p-type Cu ₂ O thin films have been devised, quality-satisfactory n-type Cu ₂ O thin films, which are difficult to prepare in principle, have not been obtained.

The present invention has been made in view of these circumstances, and one of the objects thereof is to provide a new technique for realizing n-type or i-type cuprous oxide.

In order to solve the above problems, the photoelectric conversion element of an embodiment of the present invention is provided on a p-type first semiconductor layer containing polycrystalline Cu ₂ O as a main component and a first semiconductor layer. , An n-type or i-type second semiconductor layer containing Cu ₂ O as a main component. Mn is added to the second semiconductor layer.

According to this aspect, homozygosity of cuprous oxide can be realized.

A transparent conductive layer made of zinc oxide doped with aluminum, which is formed on the second semiconductor layer, may be further provided. As a result, high conversion efficiency, which was difficult with conventional heterojunction of cuprous oxide, can be realized.

Another aspect of the present invention is a method for manufacturing a photoelectric conversion element. In this method, a step of preparing a p-type first semiconductor layer containing polycrystalline Cu ₂ O as a main component and a step of immersing the first semiconductor layer in an aqueous solution containing Mn and Cu on the first semiconductor layer. ₂ Includes a step of forming an n-type or i-type second semiconductor layer containing O as a main component.

According to this aspect, homozygotes of cuprous oxide can be easily formed.

The aqueous solution may be below 100 ° C. As a result, the second semiconductor layer can be formed at a low temperature at which water does not evaporate.

MnCl ₂ may be added to the aqueous solution. Further, the aqueous solution may have a concentration of MnCl ₂ of 1.0 × 10 ^{-5 to} 1.0 × 10 ^-1 [mol / l]. Thereby, the donor concentration of the second semiconductor layer can be set in an appropriate range.

In the step of forming the second semiconductor layer, the first semiconductor layer may be used as one electrode, and a voltage may be applied between the one electrode and the other electrode. Thereby, the growth rate of the second semiconductor layer can be controlled.

A voltage may be applied so that the current density between one electrode and the other electrode is less than 4.0 [mA / cm ² ]. As a result, a cuprous oxide thin film having high crystallinity can be formed.

The aqueous solution may be a mixture of copper sulfate, lactic acid and sodium hydroxide. As a result, an n-type or i-type second semiconductor layer containing Cu ₂ O as a main component can be formed with an inexpensive material.

It should be noted that any combination of the above components and the conversion of the expression of the present invention between methods, devices, systems and the like are also effective as aspects of the present invention. Further, an appropriate combination of the above-mentioned elements may be included in the scope of the invention for which protection by the patent is sought by the present patent application.

According to the present invention, homozygosity of cuprous oxide can be realized.

It is the schematic sectional drawing which shows the structure of the photoelectric conversion element which concerns on 1st Embodiment. It is the schematic of the film forming apparatus by the ECD method. FIG. 3A is a diagram showing a surface SEM photograph of p ^{+ type} Cu ₂ O: Na sheet, and FIG. 3 (b) is a surface SEM of p type Cu ₂ O thin film / p ^{+ type} Cu ₂ O: Na sheet. It is a figure which shows the photograph. FIG. 4 (a) is a diagram showing an X-ray diffraction (XRD) pattern of a p ^{+ type} Cu ₂ O: Na sheet, and FIG. 4 (b) is a p type Cu ₂ O thin film / p ^{+ type} Cu ₂ O: Na. The figure which shows the X-ray diffraction (XRD) pattern of a sheet, FIG. 4C is the figure which shows the X-ray diffraction (XRD) pattern of a p-type Cu ₂ O thin film / FTO / glass. It is a schematic diagram which showed the crystal structure of Cu ₂ O. 6 (a) to 6 (c) are views showing surface SEM photographs of p-type Cu ₂ O thin films formed on p ^{+ -type} Cu ₂ O: Na sheets at different current densities. FIG. 7A is a diagram showing an X-ray diffraction pattern when a p-type Cu ₂ O thin film is formed on a p ^{+ type} Cu ₂ O: Na sheet with a current density of 0.25 [mA / cm ² ]. FIG. 7 (b) is a diagram showing an X-ray diffraction pattern when a p-type Cu ₂ O thin film is formed on a p ^{+ type} Cu ₂ O: Na sheet with a current density of 1.0 [mA / cm ² ]. FIG. (C) is a diagram showing an X-ray diffraction pattern when a p-type Cu ₂ O thin film is formed on a p ^{+ type} Cu ₂ O: Na sheet with a current density of 4.0 [mA / cm ² ]. It is a figure which showed the wavelength dependence of the external quantum efficiency (EQE) of two heterojunction solar cells having different hole densities and the homojunction solar cell which concerns on 2nd Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted as appropriate.

(First Embodiment)
The present inventors are studying a solar cell using a p-type polycrystalline Cu ₂ O (copper oxide) sheet produced by thermally oxidizing a Cu (copper) sheet at a high temperature as an active layer. Cu ₂ O crystals are naturally produced and can be easily produced by using many crystal growth methods, but the pores of the introduced Cu act as acceptors and exhibit p-type conduction regardless of the method. , It was difficult to prepare n-type Cu ₂ O crystals.

Therefore, Cu in the study of solar cells using 2 _O, heterojunction comprising a combination of an n-type semiconductor composed of a material other than p-type Cu 2 _O and Cu 2 _O is widely used. Recently, the technique devised by the present inventors has realized a high conversion efficiency of 8.1 [%] in a heterojunction solar cell using p-type Cu ₂ O as an active layer. This value is close to the theoretical limit of efficiency that can be achieved with this type of solar cell. On the other hand, in a Cu ₂ O pn junction solar cell having an energy gap of 2 [eV], a conversion efficiency of about 20 [%] can be theoretically expected.

However, in order to realize this, it is important to realize an n-type Cu ₂ O layer. Therefore, as a first step for realizing the high-quality n-type Cu 2 _O layer which can be used as the active layer of the solar cell, in the first embodiment, a method for manufacturing a new active layer. In this production method, a Cu ₂ O thin film is homoepitaxially grown on a high-quality p-type Cu ₂ O sheet devised by the inventors of the present application by using an Electro Chemical deposition (ECD) method. ..

[Photoelectric conversion element]
FIG. 1 is a schematic cross-sectional view showing the configuration of the photoelectric conversion element according to the first embodiment. The photoelectric conversion element 10 is a sheet-shaped p-type semiconductor substrate 12 made of polycrystalline Cu ₂ O (copper oxide) to which Na (sodium) is added as a metal element, and a p-type semiconductor substrate 12 on one surface. a p-type Cu ₂ O thin film 14 formed as an epitaxial layer was formed on the p-type Cu ₂ O thin film 14, the transparent conductive layer 16, the p-type semiconductor substrate 12, p-type Cu ₂ O thin film 14 A back surface electrode 18 made of Au (gold) formed on a surface opposite to the surface on which the is formed is provided.

The Cu ₂ O sheet, which is the p-type semiconductor substrate 12 according to the present embodiment, has a thickness of 10 to 1000 μm. The transparent conductive layer 16 is AZO (aluminum-doped zinc oxide).

[Manufacturing method of p-type semiconductor substrate]
Next, a method for manufacturing the p-type semiconductor substrate according to the present embodiment will be described. First, a copper plate (purity 99.96 [%]) is washed and then oxidized at about 1025 [° C.] to prepare a polycrystalline p-type Cu ₂ O sheet (thickness 200 μm) that also serves as a substrate and an active layer. To do.

Next, the Cu ₂ O sheet is heat-treated in an atmosphere in which a metal halide is present. Examples of the metal compound include metal elements such as Na, K, Li, Mg, Ca and Mn and compounds such as various halogens and carbonic acids. For example, NaCl, Na ₂ CO ₃ and KCl are preferable because of their ease of handling and availability.

In the heat treatment step according to the present embodiment, a Cu ₂ O sheet is placed together with Na ₂ CO ₃ inside an electric furnace capable of controlling the atmosphere, and the atmosphere temperature is 100 to 1000 [] in an Ar atmosphere which is an inert gas. The mixture was heat-treated at 1 to 30 [h]. As the inert gas, a rare gas other than Ar or a nitrogen gas may be appropriately used. Through such a heat treatment step, a p-type semiconductor substrate 12 made of polycrystalline Cu ₂ O is formed.

[Method of forming a p-type Cu ₂ O thin film by the ECD method]
FIG. 2 is a schematic view of a film forming apparatus by the ECD method. In the film forming apparatus 20 shown in FIG. 2, the bathtub 22 is filled with the solution 24. Solution 24 is prepared by adding sodium hydroxide to an aqueous solution of copper sulfate (CuSO ₄ : concentration 0.20 mol / L) and lactic acid (CH ₃ CH (OH) COOH: concentration 3.00 mol / L) to adjust the overall pH to 12. It has been adjusted to. A Pt sheet 26 as an anode and a p-type semiconductor substrate 12 or an FTO transparent conductive film 28 as a cathode are immersed in the solution 24.

As the p-type semiconductor substrate 12, a p ^{+ -type} Cu ₂ O: Na sheet having a hole density on the order of 10 ¹⁵ [cm ^-3 ] is used. The temperature of the solution 24 is 70 [° C.]. The temperature is measured by the thermometer 29. Further, the current density (J) is controlled by the control unit 30 so as to be a value selected in the range of 0.25 to 4.0 [mA / cm ² ]. The control unit 30 includes a power supply 32, a voltmeter 34, and an ammeter 36.

Further, in the photoelectric conversion element (AZO / p-type Cu ₂ O thin film / p ^{+ type} Cu ₂ O: Na sheet) according to Reference Example 1 in which the thin film produced by the ECD method is used as the active layer, and Comparative Example 1. The photoelectric conversion element (AZO / p-type Cu ₂ O thin film / FTO) was prepared, and the photovoltaic characteristics of each element were measured under light irradiation of AM1.5G (100 [mW / cm ² ]).

FIG. 3 (a) is a diagram showing a surface SEM photograph of p ^{+ type} Cu ₂ O: Na sheet, and FIG. 3 (b) is a view showing a p-type Cu ₂ O thin film / p ^{+ type} Cu ₂ O: surface SEM of Na sheet. It is a figure which shows the photograph. As shown in FIG. 3B, it can be seen that the p-type Cu ₂ O thin film is uniformly formed on the p ^{+ -type} Cu ₂ O: Na sheet, which is a substrate.

FIG. 4 (a) is a diagram showing an X-ray diffraction (XRD) pattern of a p ^{+ type} Cu ₂ O: Na sheet, and FIG. 4 (b) is a p type Cu ₂ O thin film / p ^{+ type} Cu ₂ O: Na. The figure which shows the X-ray diffraction (XRD) pattern of a sheet, FIG. 4C is the figure which shows the X-ray diffraction (XRD) pattern of a p-type Cu ₂ O thin film / FTO / glass. FIG. 5 is a schematic view showing the crystal structure of Cu ₂ O.

As can be seen from the diffraction peak of the XRD pattern shown in FIG. 4 (a), the p ⁺ form Cu ₂ O: Na sheet is a polycrystal preferentially oriented toward the (110) plane of the crystal structure shown in FIG. Further, as shown in FIG. 4 (b), in the p-type Cu ₂ O thin film, only the diffraction peak oriented in the (110) plane, which is the same as the orientation of the p ^{+ type} Cu ₂ O: Na sheet, was observed. On the other hand, as shown in FIG. 4C, the p-type Cu ₂ O thin film formed on the FTO thin film was not oriented in a specific plane orientation.

6 (a) to 6 (c) are views showing surface SEM photographs of p-type Cu ₂ O thin films formed on p ^{+ -type} Cu ₂ O: Na sheets at different current densities. FIG. 7A is a diagram showing an X-ray diffraction pattern when a p-type Cu ₂ O thin film is formed on a p ^{+ type} Cu ₂ O: Na sheet with a current density of 0.25 [mA / cm ² ]. FIG. 7 (b) is a diagram showing an X-ray diffraction pattern when a p-type Cu ₂ O thin film is formed on a p ^{+ type} Cu ₂ O: Na sheet with a current density of 1.0 [mA / cm ² ]. FIG. (C) is a diagram showing an X-ray diffraction pattern when a p-type Cu ₂ O thin film is formed on a p ^{+ type} Cu ₂ O: Na sheet with a current density of 4.0 [mA / cm ² ].

As is clear from FIGS. 6 (a) to 6 (c), the surface morphology of the p-type Cu ₂ O thin film depends on the current density J, and the current densities J are 0.25 [mA / cm ² ] and 1. A particularly uniform Cu ₂ O thin film could be produced in the case of 0.0 [mA / cm ² ].

As described above, the method for producing the active layer according to the present embodiment includes a step of preparing a semiconductor substrate made of polycrystalline Cu ₂ O to which Na is added as a metal element, and a step of preparing a semiconductor substrate containing at least copper ions at a temperature of less than 100 ° C. It includes a step of immersing a semiconductor substrate in an alkaline aqueous solution and epitaxially growing Cu ₂ O on the semiconductor substrate to form a Cu ₂ O thin film. As a result, an active layer of Cu ₂ O having a lower temperature and higher quality than before can be produced.

Further, in the step of forming the Cu ₂ O thin film, the growth rate of the thin film is controlled by applying a voltage between both electrodes using the p-type semiconductor substrate 12 as one electrode and the Pt sheet 26 as the other electrode. it can.

As described above, in the active layer according to the first embodiment, the p ^{+ type} Cu ₂ O thin film is preferentially oriented toward the (110) plane on the Cu ₂ O sheet by the evaluation by XRD, and homoepitaxially grows. It became clear that. Further, the current density is preferably 0.25 so that the current density is less than 4.0 [mA / cm ² ], preferably 1.0 [mA / cm ² ] or less. By setting [mA / cm ² ] ± 0.10, a high-quality Cu ₂ O thin film with high crystallinity could be produced, and by using this Cu ₂ O thin film as an active layer, an excellent solar cell could be realized. ..

(Second Embodiment)
In the first embodiment, a p-type Cu ₂ O thin film is homoepitaxially grown on a high-quality p-type Cu ₂ O sheet substrate by using an electrochemical solution deposition (ECD) method, which is a low-temperature film formation technology. It was shown that a high-quality active layer and a photoelectric conversion element (solar cell) having the active layer can be realized. However, since Cu 2 _O thin film according to the first embodiment is p-type, in order to achieve a homozygous between p-type Cu 2 _O sheet substrate, n in the p-type Cu 2 _O sheet substrate It is necessary to form a Cu ₂ O thin film in the form.

[Method for forming n-type Cu ₂ O thin film]
As the p-type semiconductor substrate 12, a Na-added p ⁺ Cu ₂ O: Na sheet having a hole density on the order of 10 ¹⁵ [cm ^-3 ] is used. The p ⁺ Cu ₂ O: Na sheet was prepared by heat-treating a p-type Cu ₂ O sheet prepared by thermal oxidation together with Na ₂ CO _{3 in an} Ar gas atmosphere at 800 [° C.] and 30 [h].

Next, in the bathtub 22 of the film forming apparatus 20 described in the first embodiment, CuSO ₄ having a concentration of 0.20 [mol / l] and CH ₃ CH (OH) having a concentration of 3.00 [mol / l] ) An aqueous solution containing COOH, MnCl ₂ having a concentration of 1.0 × 10 ^{-5 to} 1.0 × 10 ^-1 [mol / l], and NaOH for adjusting the pH to about 7.0 to 12. Meet. The prepared p-type Cu ₂ O: Na sheet was immersed therein as a cathode, and the p ⁺ Cu ₂ O: Na substrate was subjected to the same method as in the first embodiment by the electrochemical solution deposition method (ECD) method. A Cu ₂ O thin film was formed on the surface. The film forming conditions are a solution temperature of 70 [° C.], a current density of 0.25 to 4.0 [mA / cm ² ], and a Cu ₂ O thin film film thickness of 240 [nm].

The solution temperature is preferably less than 100 [° C.], more preferably about 50 to 80 [° C.]. If the temperature is too high, water will evaporate and the concentration of dissolved components will not be stable. Further, if the temperature is too low, a large amount of components are precipitated without being dissolved.

By immersing the p-type semiconductor substrate 12 in the aqueous solution containing Mn in this way, a Cu ₂ O thin film to which Mn is added can be formed on the p-type semiconductor substrate 12, so that a homojunction of cuprous oxide can be easily formed. it can. Further, since the Cu ₂ O thin film to which Mn is added can be formed by using an aqueous solution having a low temperature of less than 100 ° C., a special vacuum device or heating device is not required, and the manufacturing cost can be dramatically reduced. Further, by appropriately selecting the MnCl ₂ concentration in the aqueous solution, the donor concentration of the Cu ₂ O thin film can be set within a desired range. Further, since the aqueous solution is a mixture of copper sulfate, lactic acid, and sodium hydroxide, an n-type or i-type semiconductor thin film containing Cu ₂ O as a main component can be formed with an inexpensive material.

Next, a pulsed laser vapor deposition (PLD) method was used to prepare an AZO transparent electrode layer on a Cu ₂ O thin film under the condition that the film formation temperature was room temperature (RT).

Each element was irradiated with light of AM1.5G [100 mW / cm ² ], and the photovoltaic characteristics of the element were measured under the condition of 25 ° C. As for the photovoltaic characteristics, it was found that the current density, pH, film thickness, MnCl ₂ concentration, etc. at the time of film formation greatly affect the production conditions.

Next, the MnCl ₂ concentration dependence of the photovoltaic power characteristics will be described. FIG. 7 (a) is a diagram showing the relationship between the MnCl ₂ concentration and the open-circuit voltage (Voc), and FIG. 7 (b) is a diagram showing the relationship between the MnCl ₂ concentration and the short-circuit current density (Jsc). (C) is a diagram showing the relationship between the MnCl ₂ concentration and the curve factor (FF), and FIG. 7 (d) is a diagram showing the relationship between the MnCl ₂ concentration and the conversion efficiency (η).

The results shown in FIGS. 7 (a) to 7 (d) show that the pH of the aqueous solution at the time of film formation was 12, the temperature of the aqueous solution was 70 [° C.], and the film thickness of the Cu ₂ O thin film to be produced was 240 [nm. ]. Then, a solar cell was produced using the Cu ₂ O thin film obtained when the MnCl ₂ concentration was changed in the range of 0 to 1.0 × 10 ^-1 [mol / l] as an active layer, and each photovoltaic characteristic. Was measured.

As shown in FIG. 7A, the open end voltage (Voc) decreases as the MnCl ₂ concentration increases. Further, as shown in FIGS. 7 (b) and 7 (c), the short-circuit current density (Jsc) and the polar factor (FF) have a MnCl ₂ concentration of 1.0 × 10 ⁻ [mol / l / cm ² ]. It has decreased by the above. As a result, the conversion efficiency (η) is maximized when the MnCl ₂ concentration is 1.0 × 10 ^-4 [mol / l], the conversion efficiency (η) is 4.21 [%], and the open end voltage (Voc) is 0. We were able to achieve .78 [V].

When a Cu ₂ O thin film was prepared by the ECD method using an aqueous solution in which InCl ₃ was dissolved instead of MnCl ₂ , the conversion efficiency (η) was 5.0 × 10 ^-4 [mol / l) at an InCl ₃ concentration. ], The conversion efficiency (η) was 3.77 [%], and the open end voltage (Voc) was 0.71 [V]. As described above, it has been found that there is a possibility that an n-type or i-type Cu ₂ O thin film can be realized by adding Mn or In to the aqueous solution. In particular, it has been clarified that by using a Cu ₂ O thin film to which Mn is added, a photoelectric conversion element containing cuprous oxide as a main component and having a conversion efficiency greatly exceeding 4 [%] can be realized.

FIG. 8 is a diagram showing the wavelength dependence of the external quantum efficiency (EQE) of two heterojunction solar cells having different hole densities and a homojunction solar cell according to the second embodiment. In an element having a Cu ₂ O thin film formed by the ECD method as an active layer, such as the AZO / Cu ₂ O: Mn / Cu ₂ O: Na (p: 10 ¹⁵ ) solar cell according to the _second embodiment, As is clear from the spectrum of the black circles in FIG. 8, EQE is improved.

Further, as compared with the EQE spectra of the AZO / p-Cu ₂ O solar cell and the AZO / p-Cu ₂ O: Na solar cell, the hole density of the Cu ₂ O: Na thin film according to the _second embodiment is 10 ^It is considered to be about ¹³ [cm ^-3 ]. Therefore, it is presumed that at least i-type Cu ₂ O thin film is formed by adding Mn, and homozygosity of cuprous oxide can be realized by combining with the p—Cu ₂ O thin film.

Thus, the photoelectric conversion element according to the second embodiment includes a p-type semiconductor substrate made of Cu 2 _O in polycrystalline Na was added (first semiconductor layer), an epitaxial layer on the p-type semiconductor substrate Mn-added n-type or i-type Cu ₂ O thin film (second semiconductor layer) and aluminum-doped n-type or i-type Cu ₂ O thin film formed on the n-type or i-type Cu ₂ O thin film. A transparent conductive layer made of zinc oxide is provided. The n-type or i-type Cu ₂ O thin film preferably has a thickness of 80 nm to 800 nm. As a result, high conversion efficiency that cannot be achieved by the conventional heterojunction of Cu ₂ O can be realized.

Although the present invention has been described above with reference to the above-described embodiments, the present invention is not limited to the above-described embodiments, and the configurations of the embodiments may be appropriately combined or substituted. Those are also included in the present invention. Further, it is also possible to appropriately rearrange the combinations and the order of processes in each embodiment based on the knowledge of those skilled in the art, and to add modifications such as various design changes to each embodiment, and such modifications. The embodiment to which is added may also be included in the scope of the present invention.

10 Photoelectric conversion element, 12p type semiconductor substrate, 14 Cu ₂ O thin film, 16 transparent conductive layer, 18 back electrode, 20 film forming equipment, 22 bathtub, 24 solution, 26 Pt sheet, 28 FTO transparent conductive film, 29 thermometer , 30 Control unit, 32 power supply, 34 voltmeter, 36 ammeter.

Claims (9)

A p-type first semiconductor layer containing polycrystalline Cu ₂ O as a main component,
An n-type or i-type second semiconductor layer containing Cu ₂ O as a main component, which is provided on the first semiconductor layer, is provided.
The second semiconductor layer is a photoelectric conversion element to which Mn is added. The photoelectric conversion element according to claim 1, further comprising a transparent conductive layer made of zinc oxide doped with aluminum, which is formed on the second semiconductor layer. A step of preparing a p-type first semiconductor layer containing polycrystalline Cu ₂ O as a main component, and
A step of immersing the first semiconductor layer in an aqueous solution containing Mn to form an n-type or i-type second semiconductor layer containing Cu ₂ O as a main component on the first semiconductor layer.
A method for manufacturing a photoelectric conversion element, which comprises. The method for manufacturing a photoelectric conversion element according to claim 3, wherein the aqueous solution is less than 100 ° C. The method for manufacturing a photoelectric conversion element according to claim 3 or 4, wherein the aqueous solution contains MnCl ₂ . The method for producing a photoelectric conversion element according to claim 5, wherein the aqueous solution has a concentration of MnCl ₂ of 1.0 × 10 ^{-5 to} 1.0 × 10 ^-1 [mol / l]. Any of claims 3 to 6, wherein the step of forming the second semiconductor layer uses the first semiconductor layer as one electrode and applies a voltage between the one electrode and the other electrode. The method for manufacturing a photoelectric conversion element according to item 1. The production of the photoelectric conversion element according to claim 7, wherein a voltage is applied so that the current density between the one electrode and the other electrode is less than 4.0 [mA / cm ² ]. Method. The method for producing a photoelectric conversion element according to any one of claims 3 to 8, wherein the aqueous solution is a mixture of copper sulfate, lactic acid, and sodium hydroxide.