JP2014086519A - Process of manufacturing solar cell and solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process of manufacturing a solar cell and the solar cell, capable of improving conversion efficiency.SOLUTION: By coating a coating liquid formed by dispersing semiconductor nanoparticles that is a raw material of a light absorption layer in an organic solvent, a precursor layer 400 is formed on a substrate 11. Next, a hydrogenation catalyst layer is formed on the precursor layer 400. Next, reduction removal processing for reducing and removing impurities remaining in the precursor layer 400 is performed using the hydrogenation catalyst layer as a catalyst under hydrogen atmosphere.

Description

  The present invention relates to a solar cell manufacturing method and a solar cell.

A solar cell is a photovoltaic device that absorbs light in a light absorption layer and converts it into electrical energy. The light absorption layer is formed using a material such as a compound semiconductor in addition to silicon. For example, a light-absorbing layer is formed by a compound semiconductor (CIGS-based compound semiconductor) of IB-IIIB-VIB (group 11-12-16) having a chalcopyrite crystal structure such as Cu (In, Ga) Se _2. Is forming.

  The CIGS compound semiconductor has a large absorption coefficient for light in a wide wavelength region from the visible region to the near infrared region. For this reason, high conversion efficiency is realizable in a thin film type solar cell. In addition, there are advantages such as little deterioration over time.

  The light absorption layer of the CIGS compound semiconductor is formed by forming a precursor film and then subjecting the precursor layer to a heat treatment. The precursor layer is formed by various film forming methods such as vapor deposition, sputtering, electrodeposition, and coating. Among these, the coating method is attracting attention because it is low in cost and can realize high throughput.

  When a CIGS compound semiconductor light absorption layer is provided by a coating method, first, a coating solution is prepared. As the coating solution, for example, a solution in which an organic ligand is coordinated to an element located on the surface of the semiconductor nanoparticles and the semiconductor nanoparticles are dispersed in an organic solvent is prepared. The semiconductor nanoparticles are nano-sized fine particles and are called quantum dots. After preparing the coating solution, a precursor layer is formed by applying the coating solution. And the light absorption layer is formed by sintering the nanoparticle in a precursor layer (for example, refer patent documents 1, 2).

JP 2010-225829 A JP 2011-505449 A

  As described above, since the light absorption layer of the CIGS compound semiconductor has a large absorption coefficient, the conversion efficiency can be improved.

  However, as described above, when the light absorption layer of the CIGS compound semiconductor is provided by a coating method, it may not be easy to sufficiently improve the conversion efficiency. For example, if the organic ligand or organic solvent contained in the raw material remains as an impurity in the light absorption layer of the CIGS compound semiconductor, the conversion efficiency may decrease.

  An object of this invention is to provide the manufacturing method and solar cell of a solar cell which can improve conversion efficiency.

  A method for manufacturing a solar cell according to an embodiment of the present invention is a method for manufacturing a solar cell in which a light absorption layer is formed on a substrate, in which semiconductor nanoparticles serving as a raw material for the light absorption layer are dispersed in an organic solvent. A precursor layer forming step for forming a precursor layer on the substrate, a hydrogenation catalyst layer forming step for forming a hydrogenation catalyst layer on the precursor layer, and a remaining in the precursor layer A reduction and removal process for reducing and removing impurities to be performed using the hydrogenation catalyst layer as a catalyst in a hydrogen atmosphere.

  A solar cell according to an embodiment of the present invention includes a substrate and a light absorption layer provided on the substrate, and the light absorption layer is a coating in which semiconductor nanoparticles as a raw material are dispersed in an organic solvent. After forming a precursor layer on the substrate by applying a liquid, and forming a hydrogenation catalyst layer on the precursor layer, a reduction removal treatment for reducing and removing impurities remaining in the precursor layer is performed in a hydrogen atmosphere. It was formed by using the hydrogenation catalyst layer as a catalyst below.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and solar cell of a solar cell which can improve conversion efficiency can be provided.

Sectional drawing which shows the principal part of the solar cell which concerns on 1st Embodiment. Sectional drawing which shows the manufacturing method of the solar cell which concerns on 1st Embodiment. Sectional drawing which shows the manufacturing method of the solar cell which concerns on 1st Embodiment. The figure which shows typically the semiconductor nanoparticle contained in a coating liquid in the manufacturing method of the solar cell which concerns on 1st Embodiment. The figure which shows the transmittance | permeability of a 1st upper electrode part in the manufacturing method of the solar cell which concerns on 1st Embodiment. Sectional drawing which shows the principal part of the solar cell which concerns on 2nd Embodiment. Sectional drawing which shows the manufacturing method of the solar cell which concerns on 2nd Embodiment.

  Embodiments will be described with reference to the drawings.

(First embodiment)
[1] Configuration FIG. 1 is a cross-sectional view showing a main part of the solar cell according to the first embodiment. In FIG. 1, a unit cell is shown.

  As shown in FIG. 1, the solar cell 10 includes a substrate 11, a lower electrode 31, a light absorption layer 41, a buffer layer 51, and an upper electrode 60. The solar cell 10 receives light incident from the upper surface side where each part such as the light absorption layer 41 is provided on the substrate 11 and performs photoelectric conversion. Each part which comprises the solar cell 10 is demonstrated sequentially.

  The substrate 11 is a plate-like body having a flat surface. The substrate 11 is, for example, a glass substrate. In addition, a plate-like body such as a ceramic substrate, a resin substrate, or a metal substrate may be used as the substrate 11 as appropriate.

  The lower electrode 31 is provided on the substrate 11 as shown in FIG. The lower electrode 31 is, for example, a Mo (molybdenum) film and is formed so as to cover the flat upper surface of the substrate 11. In addition, the lower electrode 31 may be formed using a conductive material such as Al (aluminum), Ti (titanium), Ta (tantalum), Au (gold), or a plurality of different types of conductive materials. You may form by laminating | stacking a layer.

As shown in FIG. 1, the light absorption layer 41 is provided on the lower electrode 31. The light absorption layer 41 is formed so as to cover the upper surface of the lower electrode 31 above the substrate 11. The light absorption layer 41 is, for example, a semiconductor layer having a p-type conductivity, and is made of a compound semiconductor containing a group IB (group 11) element, a group IIIB (group 13) element, and a group VIB (group 16) element. Is formed. For example, CuInSe ₂ (copper indium diselenide (CIS)), Cu (In, Ga) Se ₂ (copper indium gallium selenide (CIGS)), Cu (In, Ga) (Se, S) ₂ (two It is formed of an IB-IIIB-VIB group compound semiconductor (CIGS semiconductor) having a chalcopyrite crystal structure, such as selenium, copper indium gallium sulfide (CIGSS).

As shown in FIG. 1, the buffer layer 51 is provided on the light absorption layer 41. The buffer layer 51 is formed above the substrate 11 so as to cover the upper surface of the light absorption layer 41. Unlike the light absorption layer 41, the buffer layer 51 is, for example, an n-type semiconductor layer, and is provided so as to form a pn junction with the light absorption layer 41. For example, the buffer layer 51 is made of CdS (cadmium sulfide). In addition, for the buffer layer 51, ZnO (zinc oxide), In ₂ S ₃ (indium sulfide), ZnS (zinc sulfide), In ₂ Se ₃ (indium selenide), In (OH, S), (Zn , In) (Se, OH), ZnInS, and (Zn, Mg) O may be used. That is, the buffer layer 51 is provided so as to form a heterojunction with the light absorption layer 41. The buffer layer 51 suppresses recombination of carriers at the interface between the light absorption layer 41 and the upper electrode 60.

  The upper electrode 60 is provided on the buffer layer 51 as shown in FIG. The upper electrode 60 is a TCO (Transparent Conducting Oxide) layer formed of a transparent conductive material that transmits light.

  In the present embodiment, the upper electrode 60 includes a first upper electrode part 61 and a second upper electrode part 62.

  Of the upper electrode 60, the first upper electrode portion 61 is formed above the substrate 11 so as to cover the upper surface of the buffer layer 51. Although details will be described later, the first upper electrode portion 61 is formed by oxidizing a metal that becomes a catalyst when hydrogenating impurities remaining in the precursor layer of the light absorption layer 41 provided by a coating method. Yes. For example, the first upper electrode portion 61 is a RuOx film formed by oxidizing a Ru film.

Of the upper electrode 60, the second upper electrode portion 62 is formed above the substrate 11 so as to cover the upper surface of the first upper electrode portion 61. The second upper electrode part 62 is made of a metal oxide different from that of the first upper electrode part 61. For example, the second upper electrode portion 62 is a ZnO ₂ film.

  The unit cells having the above-described parts are electrically connected in series. Specifically, the upper electrode 60 of the unit cell and the lower electrode 31 of another unit cell adjacent to the unit cell are electrically connected by a contact electrode (not shown).

[2] Manufacturing Method A method for manufacturing the solar cell 10 will be described.

  2 and 3 are cross-sectional views illustrating the method for manufacturing the solar cell according to the first embodiment. 2 and 3, the manufacturing steps are sequentially shown in (A) to (H), and the solar cell 10 shown in FIG. 1 is manufactured by performing each manufacturing step.

(A) Preparation of Substrate 11 First, the substrate 11 is prepared as shown in FIG.

  Here, as the substrate 11, for example, a glass substrate having a thickness of about 0.7 to 3.5 mm and formed of blue plate glass (soda lime glass) is prepared.

(B) Formation of Lower Electrode 31 Next, as shown in FIG. 2 (B), the lower electrode 31 is formed.

  Here, the lower electrode 31 is formed so as to cover the upper surface of the substrate 11. For example, the lower electrode 31 is formed by forming a Mo (molybdenum) film having a thickness of 500 nm or more and 1000 nm or less by a film forming method such as sputtering.

(C) Formation of Precursor Layer 400 Next, as shown in FIG. 2C, the precursor layer 400 is formed.

  Here, the precursor layer 400 is formed so as to cover the lower electrode 31 on the upper surface of the substrate 11.

  In the present embodiment, the precursor layer 400 is formed by a coating method. Specifically, a coating solution is prepared in which 50 mg to 800 mg of CIGS-based semiconductor nanoparticles that are raw materials for the light absorption layer 41 (see FIG. 1) are dispersed in 1 cc of a solvent (toluene).

  FIG. 4 is a diagram schematically showing semiconductor nanoparticles contained in a coating solution in the method for manufacturing a solar cell according to the first embodiment.

  As shown in FIG. 4, an organic ligand 421 is bonded to the surface of CIGS-based semiconductor nanoparticles 411.

CIGS-based semiconductor nanoparticles 411 are, for example, CuInSe ₂ , and a plurality of ligands 421 are coordinated to each of a plurality of Se located on the surface of the semiconductor nanoparticles 411. For example, semiconductor nanoparticles 411 having an average particle diameter of 3 nm or more and 10 nm or less are suitable.

  The ligand 421 includes, for example, phosphine (eg, trioctylphosphine, triphenolphosphine, t-butylphosphine), phosphine oxide (eg, trioctylphosphine oxide), alkylphosphonic acid, alkylamine (eg, hexadecylamine, octylamine). ), Arylamine, octane selenol, pyridine, long chain fatty acid, and thiophene having a lone pair of electrons.

  After preparing the coating solution, a coating film is formed by coating the prepared coating solution on the upper surface of the lower electrode 31 using a coating device such as a slit coater or a bar coater. Then, the precursor layer 400 is formed by volatilizing the solvent by drying the coating film at 150 ° C. to 260 ° C. for 5 minutes to 30 minutes. For example, the precursor layer 400 is formed to have a thickness of 500 nm to 2000 nm.

After performing the above drying process, for example, an “oxidation removal process” is performed under the following conditions. That is, by performing heat treatment on the precursor layer 400, impurities remaining in the precursor layer 400 are oxidized and removed from the precursor layer 400.
<Conditions for “oxidation removal treatment”>
-Atmosphere: Oxygen atmosphere (O ₂ : N ₂ = 1-10: 90-99) (mass%)
・ Processing temperature: 150 ° C or more, 350 ° C or less ・ Processing time: 1 minute or more, 30 minutes or less

In this “oxidation removal treatment”, for example, an oxidation reaction occurs as shown in the following reaction formula. Specifically, impurities such as organic ligands and organic solvents contained in the precursor layer 400 are oxidized. For this reason, the impurities remaining in the precursor layer 400 are gasified, and the oxidized impurities are released to the outside.
<Reaction formula of “oxidation removal treatment”>
C _n H _m + O ₂ → CO ₂ + H ₂ O

(D) Formation of Buffer Layer 51 Next, as shown in FIG. 2D, the buffer layer 51 is formed.

  Here, the buffer layer 51 is formed so as to cover the upper surface of the precursor layer 400 above the substrate 11. For example, the buffer layer 51 is formed by forming a CdS (cadmium sulfide) film by a film forming method such as a chemical bath deposition method or a sputtering method. For example, the buffer layer 51 is formed so that the thickness is in the range of 30 nm to 200 nm.

(E) Formation of hydrogenation catalyst layer 610 Next, as shown in FIG. 3E, a hydrogenation catalyst layer 610 is formed.

Here, the hydrogenation catalyst layer 610 is formed so as to cover the upper surface of the buffer layer 51 above the substrate 11. For example, the hydrogenation catalyst layer 610 is formed under the following conditions.
<Film Formation Conditions for Hydrogenation Catalyst Layer 610>
・ Material: Ru (ruthenium)
・ Film formation method: Sputtering method or CVD method ・ Film thickness: 1 nm or more, 5 nm or less

After the formation of the hydrogenation catalyst layer 610, for example, “reduction removal treatment” is performed under the following conditions. That is, by performing heat treatment on the precursor layer 400, impurities remaining in the precursor layer 400 are reduced and removed from the precursor layer 400.
<Conditions for “reduction removal treatment”>
Atmosphere: Hydrogen atmosphere (H ₂ : N ₂ = 3 to 100: 97 to 0) (mass%)
・ Processing temperature: 200 ℃ or more, 500 ℃ or less ・ Processing time: 5 minutes or more, 30 minutes or less

In the above “reduction removal treatment”, for example, a reduction reaction as shown in the following reaction formula occurs using the hydrogenation catalyst layer 610 as a catalyst. Specifically, the CIGS semiconductor oxidized in the “oxidation removal process” is reduced.
<Reaction removal treatment formula>
MO + H ₂ → M + H ₂ 0 (where M is Cu, In, Ga or Se)

  Then, the light absorption layer 41 is formed by performing the sintering process which sinters about the semiconductor nanoparticle 411 (refer FIG. 4) in the precursor layer 400. FIG.

Specifically, the semiconductor layer 411 (see FIG. 4) is sintered by performing heat treatment on the precursor layer 400 under the following conditions.
<Sintering conditions>
・ Sintering temperature: 350 ° C. or more and 600 ° C. or less ・ Heat treatment time: 2 minutes or more and 120 minutes or less

(F) Formation of First Upper Electrode Unit 61 Next, as shown in FIG. 3F, the first upper electrode unit 61 is formed.

Here, the first upper electrode portion 61 that is a transparent conductive film is formed by performing an oxidation treatment on the hydrogenation catalyst layer 610 formed above. For example, a ruthenium oxide (RuOx) film is formed as the first upper electrode portion 61 by oxidizing the hydrogenation catalyst layer 610 that is a ruthenium (Ru) film under the following conditions.
<Oxidation treatment of hydrogenation catalyst layer 610>
・ Atmosphere: Oxygen atmosphere (O ₂ : N ₂ = 10: 90) (mass%)
・ Processing temperature: 200 ℃ or more, 400 ℃ or less ・ Processing time: 1 minute or more, 3 minutes or less

  FIG. 5 is a diagram showing the transmittance of the first upper electrode portion 61 in the method for manufacturing a solar cell according to the first embodiment. In FIG. 5, the horizontal axis represents the processing temperature. Of the horizontal axis, “As-grown” indicates room temperature. On the other hand, the vertical axis represents the transmittance (%). FIG. 5 shows the results of the hydrogenation catalyst layer 610, which is the Ru film to be processed, formed by sputtering, and the film thickness is 5 nm and 100 nm. ing. Here, the case of light having a wavelength of 460 nm is shown.

  As shown in FIG. 5, the higher the processing temperature, the higher the transmittance of the first upper electrode portion 61 after processing. However, when the film thickness of the hydrogenation catalyst layer 610, which is the Ru film to be processed, is 5 nm, it is preferable that the transmittance is 90% or more regardless of the processing temperature. At the same time, from the viewpoint of securing device characteristics and the like, the above processing temperature is preferably 200 ° C. or higher and 400 ° C. or lower.

(G) Formation of Second Upper Electrode Part 62 Next, as shown in FIG. 1, the second upper electrode part 62 is formed.

Here, the second upper electrode portion 62 is formed above the substrate 11 so as to cover the upper surface of the first upper electrode portion 61. For example, the second upper electrode portion 62 of the zinc peroxide film (ZnO ₂ ) is formed by performing a heat treatment after forming a zinc oxide film (ZnO) under the following conditions.
<Deposition conditions for zinc oxide film (ZnO)>
-Film formation method: Sputtering method or CVD method-Film thickness: 100 nm or more and 400 nm or less <Heat treatment conditions for zinc oxide film (ZnO)>
・ Atmosphere: Oxygen atmosphere (O ₂ : N ₂ = 10: 90) (mass%)
・ Processing temperature ... 200 ℃ ~ 250 ℃
・ Processing time: 1 minute or more, 30 minutes or less

  Then, the solar cell 10 is completed through processes, such as connecting between unit cells electrically in series using a contact electrode (not shown).

[3] Summary As described above, in the present embodiment, the precursor layer 400 is formed above the substrate 11 by applying a coating liquid in which the semiconductor nanoparticles 411 serving as the raw material of the light absorption layer 41 are dispersed in an organic solvent. Form. An “oxidation removal process” for removing impurities remaining in the precursor layer 400 by oxidizing is performed in an oxygen atmosphere. After the “oxidation removal process”, a hydrogenation catalyst layer 610 is formed above the precursor layer 400. Then, a “reduction removal process” for removing impurities remaining in the precursor layer 400 by reducing is performed using the hydrogenation catalyst layer 610 as a catalyst in a hydrogen atmosphere.

  Therefore, in this embodiment, impurities such as organic ligands and organic solvents remaining in the light absorption layer 41 of the CIGS compound semiconductor can be sufficiently removed, so that the conversion efficiency of the solar cell can be improved. Specifically, the conversion efficiency can be improved by 2 to 5%. Along with this, cost reduction can be easily realized.

  In the present embodiment, the buffer layer 51 is formed on the precursor layer 400. Then, the hydrogenation catalyst layer 610 is formed so as to be stacked on the buffer layer 51. Here, a Ru (ruthenium) film is formed as the hydrogenation catalyst layer 610. Then, after performing the reduction and removal treatment, the hydrogenation catalyst layer 610 is oxidized to form the first upper electrode portion 61 that is a transparent conductive layer. That is, the ruthenium oxide film is formed as the first upper electrode portion 61 by oxidizing the hydrogenation catalyst layer 610 that is a Ru (ruthenium) film.

  Thus, in this embodiment, since the 1st upper electrode part 61 which comprises the upper electrode 60 is formed with the hydrogenation catalyst layer 610, the process of removing the hydrogenation catalyst layer 610 can be skipped.

(Second Embodiment)
[1] Configuration FIG. 6 is a cross-sectional view showing a main part of a solar cell according to the second embodiment. In FIG. 6, unit cells are shown as in FIG.

  As shown in FIG. 6, the present embodiment is different from the first embodiment in the upper electrode 60b. The present embodiment is the same as the case of the first embodiment except for this point and points related thereto. For this reason, in this embodiment, the description overlapping with the above embodiment is omitted as appropriate.

  The upper electrode 60b is formed of a single layer as shown in FIG. Unlike the case of the first embodiment, the upper electrode 60b does not include a plurality of layers. The upper electrode 60b is a TCO layer and is formed using a transparent conductive material such as ZnOAl.

[2] Manufacturing Method A method for manufacturing the solar cell 10b will be described.

  FIG. 7 is a cross-sectional view illustrating a method for manufacturing a solar cell according to the second embodiment. In FIG. 7, each manufacturing process is shown in order from (A) to (C).

  In this embodiment, before performing each manufacturing process shown in FIG. 7, as in the case of the first embodiment, the substrate 11 is prepared (see FIG. 2A), and the lower electrode 31 is formed (see FIG. B)) and the formation of the precursor layer 400 (see FIG. 2C). That is, in the manufacturing method according to the first embodiment, the manufacturing steps up to “oxidation removal process” for oxidizing and removing impurities remaining in the precursor layer 400 are performed. Then, the solar cell 10b shown in FIG. 6 is manufactured by performing each manufacturing process shown in FIG. Each manufacturing process will be shown sequentially.

(A) Formation of Silicon Oxide Film 600 As shown in FIG. 7A, a silicon oxide film 600 is formed.

Here, a silicon oxide film 600 is formed above the substrate 11 so as to cover the upper surface of the precursor layer 400. For example, the silicon oxide film 600 is formed under the following conditions.
<Deposition Conditions for Silicon Oxide Film 600>
・ Film formation method: Sputter method ・ Film thickness: 1 nm or more, 10 nm or less

(B) Formation of hydrogenation catalyst layer 610 Next, as shown in FIG. 7B, a hydrogenation catalyst layer 610 is formed.

  Here, for example, a Ru (ruthenium) film is formed as the hydrogenation catalyst layer 610 so as to cover the upper surface of the silicon oxide film 600 above the substrate 11 as in the case of the first embodiment.

  Then, after the formation of the hydrogenation catalyst layer 610, as in the case of the first embodiment, “reduction removal treatment” is performed to remove impurities remaining in the precursor layer 400.

  Thereafter, similarly to the case of the first embodiment, the light absorption layer 41 is formed by executing a sintering process for sintering the semiconductor nanoparticles 411 (see FIG. 4) in the precursor layer 400.

(C) Removal of Silicon Oxide Film 600 and Hydrogenation Catalyst Layer 610 Next, as shown in FIG. 7C, the silicon oxide film 600 and the hydrogenation catalyst layer 610 are removed.

  Here, for example, both the silicon oxide film 600 and the hydrogenation catalyst layer 610 are simultaneously removed using hydrofluoric acid (HF). Thereby, the upper surface of the light absorption layer 41 is exposed.

(D) Formation of Buffer Layer 51 and Upper Electrode 60b Next, as shown in FIG. 6, the buffer layer 51 and the upper electrode 60b are formed.

  Here, the buffer layer 51 is formed so as to cover the upper surface of the light absorption layer 41 above the substrate 11. For example, the buffer layer 51 is formed under the same conditions as in the first embodiment.

  After the formation of the buffer layer 51, the upper electrode 60b is formed so as to cover the upper surface of the buffer layer 51 above the substrate 11. For example, the upper electrode 60b is formed by depositing a transparent conductive material such as ZnOAl by a deposition method such as sputtering, vapor deposition, or CVD. For example, the upper electrode 60b is formed so that the thickness is in the range of 0.05 μm or more and 3.0 μm or less.

  Then, the solar cell 10b is completed through processes, such as connecting between unit cells electrically in series using a contact electrode (not shown).

[3] Summary As described above, in the present embodiment, the “oxidation removal process” and the “reduction removal process” are performed as in the case of the first embodiment.

  Accordingly, in the present embodiment, as in the case of the first embodiment, impurities such as organic ligands and organic solvents remaining in the light absorption layer 41 of the CIGS compound semiconductor can be sufficiently removed. Effects such as improvement in conversion efficiency can be achieved.

  In this embodiment, after the silicon oxide film 600 is formed on the precursor layer 400, the hydrogenation catalyst layer 610 is formed so as to be stacked on the silicon oxide film 600. Therefore, after the reduction and removal treatment, both the silicon oxide film 600 and the hydrogenation catalyst layer 610 can be removed using hydrofluoric acid (HF). Therefore, this embodiment can improve manufacturing efficiency.

[4] Others In this embodiment, the case where a Ru (ruthenium) film is formed as the hydrogenation catalyst layer 610 has been described. However, the present invention is not limited to this. In the present embodiment, the hydrogenation catalyst layer 610 is removed, and the hydrogenation catalyst layer 610 is left and oxidized as in the first embodiment, so that the first upper electrode portion 61 (a transparent conductive layer) ( (See FIG. 3 and the like). For this reason, in this embodiment, in addition to the Ru (ruthenium) film, a metal that becomes a catalyst in the catalytic hydrogenation reaction, such as Pt (platinum), Ni (nickel), Pd (palladium), etc. A catalyst layer 610 may be formed.

  In this embodiment, the case where the hydrogenation catalyst layer 610 is formed so as to be stacked on the silicon oxide film 600 after the silicon oxide film 600 is formed on the precursor layer 400 is described, but the present invention is not limited to this. The hydrogenation catalyst layer 610 may be formed directly on the precursor layer 400 without forming the silicon oxide film 600 on the precursor layer 400. In this case, for example, the hydrogenation catalyst layer 610 is removed by dry etching.

(Third embodiment)
[1] Manufacturing Method, etc. In the present embodiment, the “oxidation removal process” is not performed in the manufacturing method in the second embodiment. This embodiment is the same as the case of the second embodiment except for this point and points related thereto. For this reason, in this embodiment, the description overlapping with the above embodiment is omitted as appropriate.

  In the present embodiment, as in the second embodiment, the substrate 11 is prepared (see FIG. 2A), the lower electrode 31 is formed (see FIG. 2B), and the precursor layer 400 is formed. (See FIG. 2C). Here, unlike the case of the second embodiment, the “oxidation removal process” for oxidizing and removing impurities remaining in the precursor layer 400 is not performed, but the process up to the “oxidation removal process” is performed.

  Thereafter, as in the case of the second embodiment, a silicon oxide film 600 is formed (see FIG. 7A) and a hydrogenation catalyst layer 610 is formed (see FIG. 7B). That is, in the formation of the hydrogenation catalyst layer 610, for example, a Ru (ruthenium) film is formed as the hydrogenation catalyst layer 610 so as to cover the upper surface of the silicon oxide film 600 above the substrate 11. Thereafter, by performing “reduction removal treatment”, impurities remaining in the precursor layer 400 are removed.

In the “reduction removal treatment” of this embodiment, for example, a reduction reaction as shown in the following reaction formula occurs using the hydrogenation catalyst layer 610 as a catalyst. As a result, impurities such as organic ligands and organic solvents contained in the precursor layer 400 are reduced. For this reason, the impurities remaining in the precursor layer 400 are gasified, and the reduced impurities are released to the outside.
<Reaction removal treatment formula>
・ C + nH ^* → CHn

  After performing the above “reduction removal process”, as in the case of the second embodiment, the silicon oxide film 600 and the hydrogenation catalyst layer 610 are removed (see FIG. 7C), the buffer layer 51 and the upper part are removed. The electrode 60b is formed (see FIG. 6). And the solar cell 10b is completed through processes, such as connecting between unit cells electrically in series using a contact electrode (not shown).

[2] Summary As described above, in this embodiment, the “reduction removal process” is performed as in the case of the second embodiment.

  Therefore, in this embodiment, since the impurities remaining in the light absorption layer 41 of the CIGS compound semiconductor can be sufficiently removed, the conversion efficiency of the solar cell can be improved.

  Although an example of the embodiment has been described above, the present invention is not limited to this, and various modifications can be adopted.

  For example, in the above embodiment, the case where the buffer layer 51 is provided has been described, but the present invention is not limited to this. The solar cell 10 may be configured such that a pn junction or a Schottky junction is formed between the light absorption layer 41 and the upper electrode 60 without providing the buffer layer 51.

DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 31 ... Lower electrode, 41 ... Light absorption layer, 51 ... Buffer layer, 60 ... Upper electrode, 60b ... Upper electrode, 61 ... 1st upper electrode part, 62 ... 2nd upper electrode part, 400 ... Precursor layer 411 ... Semiconductor nanoparticles, 422 ... Ligand, 600 ... Silicon oxide film, 610 ... Hydrogenation catalyst layer

Claims (5)

A method for manufacturing a solar cell in which a light absorption layer is formed on a substrate,
A precursor layer forming step of forming a precursor layer on the substrate by applying a coating liquid in which semiconductor nanoparticles serving as a raw material of the light absorption layer are dispersed in an organic solvent;
A hydrogenation catalyst layer forming step of forming a hydrogenation catalyst layer on the precursor layer;
A reduction and removal treatment step of reducing and removing impurities remaining in the precursor layer by using the hydrogenation catalyst layer as a catalyst in a hydrogen atmosphere.
A method for manufacturing a solar cell. An oxidation removal treatment step in which an oxidation removal treatment for oxidizing and removing impurities remaining in the precursor layer is performed in an oxygen atmosphere;
The oxidation removal treatment step is performed before the hydrogenation catalyst layer formation step,
The manufacturing method of the solar cell of Claim 1. Forming a buffer layer on the precursor layer,
In the hydrogenation catalyst layer forming step, the hydrogenation catalyst layer is formed so as to be laminated on the buffer layer,
A transparent conductive layer is formed by oxidizing the hydrogenation catalyst layer after performing the reduction and removal treatment step,
The manufacturing method of the solar cell of Claim 1 or Claim 2. Forming a silicon oxide film on the precursor layer,
In the hydrogenation catalyst layer forming step, the hydrogenation catalyst layer is formed so as to be laminated on the silicon oxide film,
After the reduction and removal treatment step, the silicon oxide film and the hydrogenation catalyst layer are removed,
The manufacturing method of the solar cell of Claim 1 or 2. A substrate and a light absorption layer provided on the substrate,
The light absorbing layer forms a precursor layer on the substrate by applying a coating liquid in which semiconductor nanoparticles as a raw material are dispersed in an organic solvent, and after forming a hydrogenation catalyst layer on the precursor layer, The reduction removal treatment for reducing and removing impurities remaining in the precursor layer is performed by using the hydrogenation catalyst layer as a catalyst in a hydrogen atmosphere,
Solar cell.

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