CN110957393B - Preparation method of light absorption layer of thin-film solar cell - Google Patents
Preparation method of light absorption layer of thin-film solar cell Download PDFInfo
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- CN110957393B CN110957393B CN201911290658.XA CN201911290658A CN110957393B CN 110957393 B CN110957393 B CN 110957393B CN 201911290658 A CN201911290658 A CN 201911290658A CN 110957393 B CN110957393 B CN 110957393B
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- 239000010409 thin film Substances 0.000 title claims abstract description 41
- 230000031700 light absorption Effects 0.000 title claims abstract description 30
- 238000002360 preparation method Methods 0.000 title abstract description 11
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 claims abstract description 91
- 229910052733 gallium Inorganic materials 0.000 claims abstract description 91
- 229910052711 selenium Inorganic materials 0.000 claims abstract description 91
- 239000011669 selenium Substances 0.000 claims abstract description 91
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims abstract description 86
- HVMJUDPAXRRVQO-UHFFFAOYSA-N copper indium Chemical compound [Cu].[In] HVMJUDPAXRRVQO-UHFFFAOYSA-N 0.000 claims abstract description 66
- 239000007789 gas Substances 0.000 claims abstract description 63
- 238000000137 annealing Methods 0.000 claims abstract description 48
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 claims abstract description 47
- 229910000037 hydrogen sulfide Inorganic materials 0.000 claims abstract description 47
- KTSFMFGEAAANTF-UHFFFAOYSA-N [Cu].[Se].[Se].[In] Chemical compound [Cu].[Se].[Se].[In] KTSFMFGEAAANTF-UHFFFAOYSA-N 0.000 claims abstract description 21
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- 239000010408 film Substances 0.000 claims abstract description 14
- 238000005507 spraying Methods 0.000 claims abstract description 13
- 238000004321 preservation Methods 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 39
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 32
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 16
- 229910052802 copper Inorganic materials 0.000 claims description 16
- 239000010949 copper Substances 0.000 claims description 16
- 229910052757 nitrogen Inorganic materials 0.000 claims description 16
- 229910052738 indium Inorganic materials 0.000 claims description 9
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 9
- 238000005086 pumping Methods 0.000 claims description 7
- 238000000151 deposition Methods 0.000 claims description 6
- 238000001704 evaporation Methods 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 4
- 238000001755 magnetron sputter deposition Methods 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 3
- 230000001681 protective effect Effects 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 abstract description 13
- 229910052717 sulfur Inorganic materials 0.000 abstract description 11
- 239000011593 sulfur Substances 0.000 abstract description 11
- 238000004073 vulcanization Methods 0.000 abstract description 8
- CDZGJSREWGPJMG-UHFFFAOYSA-N copper gallium Chemical compound [Cu].[Ga] CDZGJSREWGPJMG-UHFFFAOYSA-N 0.000 abstract description 3
- 238000006243 chemical reaction Methods 0.000 description 22
- 238000005987 sulfurization reaction Methods 0.000 description 12
- 238000004544 sputter deposition Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 7
- 239000013078 crystal Substances 0.000 description 6
- 230000007547 defect Effects 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 239000002243 precursor Substances 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- WUPHOULIZUERAE-UHFFFAOYSA-N 3-(oxolan-2-yl)propanoic acid Chemical compound OC(=O)CCC1CCCO1 WUPHOULIZUERAE-UHFFFAOYSA-N 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- 239000005864 Sulphur Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 2
- 238000010549 co-Evaporation Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- SPVXKVOXSXTJOY-UHFFFAOYSA-N selane Chemical compound [SeH2] SPVXKVOXSXTJOY-UHFFFAOYSA-N 0.000 description 2
- 229910000058 selane Inorganic materials 0.000 description 2
- 239000002341 toxic gas Substances 0.000 description 2
- 239000011787 zinc oxide Substances 0.000 description 2
- 206010039921 Selenium deficiency Diseases 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- QNWMNMIVDYETIG-UHFFFAOYSA-N gallium(ii) selenide Chemical compound [Se]=[Ga] QNWMNMIVDYETIG-UHFFFAOYSA-N 0.000 description 1
- 230000009931 harmful effect Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 238000005201 scrubbing Methods 0.000 description 1
- 239000005361 soda-lime glass Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000002207 thermal evaporation Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
- H01L31/0264—Inorganic materials
- H01L31/032—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312
- H01L31/0322—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
- H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
- H01L31/072—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
- H01L31/0749—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type including a AIBIIICVI compound, e.g. CdS/CulnSe2 [CIS] heterojunction solar cells
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention discloses a preparation method of a light absorption layer of a thin-film solar cell, which comprises the following steps: preparing a copper indium gallium prefabricated layer; preparing a selenium film layer on the copper indium gallium prefabricated layer, wherein the molar ratio of the sum of selenium and copper gallium is more than 1; placing the copper indium gallium prefabricated layer in an annealing furnace, heating to a first preset temperature, and keeping the temperature for a first preset time; heating the copper indium gallium prefabricated layer from the first preset temperature to the second preset temperature, and then keeping the temperature for the second preset time to selenize the prefabricated layer; introducing hydrogen sulfide gas through a spraying device arranged in the annealing furnace, so that excessive selenium steam in the annealing furnace is discharged and the hydrogen sulfide gas is stored; and keeping the copper indium gallium selenide prefabricated layer at the second preset temperature for heat preservation for third preset time to realize vulcanization, and preparing the copper indium gallium selenide sulfur light absorption layer. According to the invention, the selenization and the vulcanization of the copper indium gallium prefabricated layer are carried out step by step, the excessive selenization and the non-uniformity are avoided, the vulcanization quality is ensured, and the quality of the light absorption layer is improved.
Description
Technical Field
The invention belongs to the technical field of solar cells, and particularly relates to a preparation method of a light absorption layer of a thin-film solar cell.
Background
The Copper Indium Gallium Selenide (CIGS) thin film solar cell is a high-efficiency thin film solar cell and has the advantages of high stability, low cost and long service life. The copper indium gallium selenide thin-film solar cell is essentially a direct band gap semiconductor, and the basic structure of the copper indium gallium selenide thin-film solar cell comprises a substrate, a back electrode, a light absorption layer, a buffer layer, a window layer, an antireflection layer and a metal electrode layer which are sequentially stacked, wherein the photoelectric absorption layer is a compound semiconductor thin film consisting of four elements of copper, indium, gallium and selenium. At present, methods for preparing the CIGS light absorption layer mainly comprise a co-evaporation method and a sputtering selenization method, and the sputtering selenization method is widely applied to the production process of large-size batteries because the cost of the sputtering selenization method is lower than that of the co-evaporation method.
The sputtering selenization method is that a semiconductor prefabricated layer of copper indium gallium is sputtered and deposited on a substrate, then the semiconductor prefabricated layer is placed in an atmosphere containing hydrogen selenide or selenium steam for annealing, so that four elements of copper, indium, gallium and selenium are mutually reacted and crystallized, and the copper indium gallium selenide film which accords with the stoichiometric ratio is obtained. The selenization treatment is a core process of a sputtering selenization method, and the selenization environment is very critical to preparing a high-quality absorption layer film. Usually, in order to prevent the excessive selenization in the preparation process, the content of the selenium element participating in the reaction needs to be calculated, and then the corresponding high-temperature selenium vapor is introduced or the selenium element is added in advance in the reaction system. In the actual process, sufficient selenium is required to be introduced as far as possible to ensure that the vapor pressure of the selenium is sufficient in the reaction process, so as to ensure that the reaction is carried out efficiently and a copper indium gallium selenide absorption layer with excellent crystallization and size is formed. Since selenium plays a crucial role in the film quality formation period, and in the preparation of large-size films, the dosage of selenium is difficult to calculate accurately in advance due to the reaction volume, so that sufficient selenium is required to be introduced in excess or in real time before the reaction in order to ensure that sufficient selenium is available in the reaction at all times during the reaction process. Can guarantee more effectual going on of reaction process through the mode that increases selenium element, also can bring harmful effects simultaneously: the excessive selenium element can continuously corrode the back electrode after the selenization process is finished, so that the battery loss or failure is caused.
Generally, sulfurization is also performed in the sputtering selenization process route, the purpose of sulfurization is to allow sulfur to enter the vacancy where selenium exists, to compensate for defects, and the introduction of sulfur also can increase the forbidden bandwidth, so that the forbidden bandwidth of the whole light absorption layer is in a V-shaped (as shown in fig. 1), also called a U-shaped gradient distribution, that is, the forbidden bandwidth of the two side surfaces of the light absorption layer is higher than the forbidden bandwidth inside the light absorption layer, thereby achieving the effect of increasing the open-circuit voltage and further increasing the photoelectric conversion rate. The introduction of the sulfur source mainly comprises the introduction of hydrogen sulfide gas, the thermal evaporation of solid sulfur and gas selenium at present, wherein the hydrogen sulfide gas is adopted, so that the activity is high, and the effect is obvious.
At present, selenizing and vulcanizing processes after sputtering are carried out synchronously, and specifically comprise the following steps: firstly, evaporating a selenium thin film layer on a copper indium gallium prefabricated layer to form a copper indium gallium selenium precursor; then placing the prepared copper indium gallium selenide precursor into an annealing furnace for preheating, wherein the preheating temperature is 80-200 ℃, and the surface of the precursor is flattened; then, introducing hydrogen sulfide gas at the preheating temperature; and finally, heating to 500-600 ℃ in the nitrogen protection atmosphere, and simultaneously selenizing and vulcanizing the copper indium gallium selenide precursor to form the copper indium gallium selenide sulfide (CIGSSe) light absorption layer. In the high-temperature selenizing and vulcanizing process, although the sulfurization can be effectively carried out and the forbidden bandwidth is increased, the selenizing and vulcanizing processes cannot be respectively and accurately controlled, the selenium element is diffused quickly at high temperature, the random factor is large, the excessive selenium can also cause adverse effect on the sulfurization, the selenizing and vulcanizing degree of each film area is different, the uniformity and the repeatability of the film are poor, and the quality of the light absorption layer in the industrial production is difficult to ensure. Meanwhile, by adopting the one-step selenylation and sulfurization process, although the process is simple and saves time, the activity of sulfur at high temperature is high, and a large amount of sulfur can enter the copper indium gallium selenide absorption layer by virtue of sulfurization and selenylation at the same time, so that the forbidden bandwidth inside the copper indium gallium selenide absorption layer is increased, and therefore, the forbidden bandwidth of the whole light absorption layer cannot reach the acknowledged optimal V-shaped distribution, and the photoelectric conversion rate of the thin film battery can be reduced.
Disclosure of Invention
In view of the defects in the prior art, the invention provides a preparation method of a light absorption layer of a thin-film solar cell, so as to improve the quality of the light absorption layer of the thin-film solar cell and further improve the photoelectric conversion rate of the cell.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a light absorption layer of a thin film solar cell comprises the following steps:
preparing a copper indium gallium prefabricated layer by applying a magnetron sputtering process;
evaporating and depositing on the copper indium gallium prefabricated layer to form a selenium thin film layer, wherein the molar ratio of selenium in the selenium thin film layer to the sum of copper and gallium in the copper indium gallium prefabricated layer is more than 1;
placing the copper indium gallium prefabricated layer on which the selenium thin film layer is formed in an annealing furnace;
heating the copper indium gallium prefabricated layer to a first preset temperature and then keeping the temperature for a first preset time;
heating the copper indium gallium prefabricated layer from the first preset temperature to a second preset temperature, and keeping the temperature for a second preset time to selenize the copper indium gallium prefabricated layer;
introducing hydrogen sulfide gas from the upper part of the copper indium gallium prefabricated layer after selenization is finished through a spraying device arranged in the annealing furnace, so that excessive selenium steam in the annealing furnace is discharged and the hydrogen sulfide gas is stored;
and maintaining the copper indium gallium prefabricated layer at the second preset temperature for heat preservation for third preset time so as to vulcanize the copper indium gallium prefabricated layer and prepare the copper indium gallium selenide sulfide light absorption layer.
Preferably, the first preset temperature is 80-200 ℃, and the first preset time is 1-3 min; the second preset temperature is 500-600 ℃, the second preset time is 0.5-3 min, and the third preset time is 2-5 min.
Preferably, the time for heating the copper indium gallium prefabricated layer from room temperature to the first preset temperature is 0.5min to 1min, and the time for heating the copper indium gallium prefabricated layer from the first preset temperature to the second preset temperature is 3min to 5 min.
Preferably, the gas introduced through the spraying device is a mixed gas of hydrogen sulfide and nitrogen, wherein the volume concentration of the hydrogen sulfide in the mixed gas is 2-20%, and the introduction rate of the mixed gas is 0.2sccm/cm2～2sccm/cm2。
Preferably, a mixed gas of hydrogen sulfide and nitrogen is also introduced into the annealing furnace in the first preset time, wherein the introduced gasThe rate of the bulk is 0.2sccm/cm2～2sccm/cm2The volume concentration of the hydrogen sulfide is 0.5-3%.
Preferably, after the copper indium gallium prefabricated layer deposited with the selenium thin film layer is placed in an annealing furnace, firstly, a chamber of the annealing furnace is subjected to gas washing treatment and then vacuum pumping treatment, and then, the chamber is heated to the first preset temperature; naturally cooling to a third preset temperature after the heat preservation is finished until the third preset time is finished, then firstly carrying out vacuum-pumping treatment on the chamber of the annealing furnace at the third preset temperature, then introducing nitrogen protective gas until the chamber is cooled to a fourth preset temperature, and taking out the prepared product from the annealing furnace at the fourth preset temperature.
Preferably, the third predetermined temperature is 200 ℃ to 300 ℃, and the fourth predetermined temperature is 70 ℃ to 90 ℃.
Preferably, in the copper indium gallium prefabricated layer, the molar ratio of the sum of copper and indium gallium is 0.9-0.95, and the molar ratio of the sum of gallium and indium gallium is 0.1-0.3.
Preferably, the molar ratio of the selenium in the selenium thin film layer to the sum of the copper and the gallium in the copper-indium-gallium prefabricated layer is 1.6-2.2.
Preferably, the thickness of the selenium thin film layer is 700 nm-1000 nm.
According to the preparation method of the light absorption layer of the thin-film solar cell, provided by the embodiment of the invention, the molar ratio of selenium in the selenium thin-film layer to the sum of copper and gallium in the copper-indium-gallium prefabricated layer is more than 1, namely the selenium is excessive, and the excessive selenium is used for selenizing, so that the crystallization quality of copper-indium-gallium-selenium (CIGSe) is improved. And the mode of letting in hydrogen sulfide gas through spray set makes the excessive selenium vapour in the annealing furnace be discharged and has preserved hydrogen sulfide gas again after the selenization, carries out the vulcanization technology this moment again, promptly, the selenization and the vulcanization of copper indium gallium prefabricated layer go on step by step, has controlled the reaction competition of selenium and sulphur, with excessive and the inhomogeneity of avoiding the selenization, has also guaranteed the quality of vulcanizing simultaneously, improves the quality of light absorbing layer, and then promotes the photoelectric conversion rate of battery. The mode of introducing hydrogen sulfide gas through the spraying device is used for discharging excessive selenium steam, so that the selenium steam can be effectively discharged, the stable pressure intensity in the annealing furnace can be kept, and the defect caused by decomposition of the copper indium gallium prefabricated layer due to too low air pressure under the condition of high temperature is avoided.
Drawings
Fig. 1 is an exemplary illustration in which the forbidden band width of the light absorbing layer is in a V-shaped gradient distribution;
FIG. 2 is a flowchart of a method for manufacturing a light absorbing layer of a thin film solar cell according to the present invention;
FIG. 3 is a graph of annealing temperature versus time for a selenization process in accordance with an embodiment of the present invention;
FIG. 4 is an I-V plot of a solar cell prepared according to an embodiment of the present invention;
fig. 5 is an SEM image of a cross-section of a solar cell prepared according to an embodiment of the present invention.
Detailed Description
To make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the invention shown in the drawings and described in accordance with the drawings are exemplary only, and the invention is not limited to these embodiments.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present invention are shown in the drawings, and other details not so relevant to the present invention are omitted.
The invention provides a preparation method of a light absorption layer of a thin film solar cell, as shown in figure 2, the preparation method comprises the following steps:
s10, preparing the copper indium gallium prefabricated layer by applying a magnetron sputtering process.
Specifically, the alloy elements forming the copper indium gallium prefabricated layer are sputtered on a deposition substrate (such as a back electrode of a solar cell) in a vacuum environment by a magnetron sputtering method to obtain an alloy film, so that the copper indium gallium prefabricated layer is formed. Preferably, in the copper indium gallium prefabricated layer, the molar ratio of the sum of copper and indium gallium is 0.9-0.95, and the molar ratio of the sum of gallium and indium gallium is 0.1-0.3.
S20, evaporating and depositing the copper indium gallium prefabricated layer to form a selenium thin film layer, wherein the molar ratio of selenium in the selenium thin film layer to the sum of copper and gallium in the copper indium gallium prefabricated layer is larger than 1.
Specifically, solid selenium is used as a selenium source, and a selenium thin film layer is obtained on the copper indium gallium prefabricated layer through evaporation. Wherein the thickness of the selenium thin film layer is preferably 700nm to 1000 nm. Solid selenium is used as a selenium source, so that the use of hydrogen selenide highly toxic gas is avoided, and the safety in the production process is ensured.
The molar ratio of selenium in the selenium thin film layer to the sum of copper and gallium in the copper-indium-gallium prefabricated layer is larger than 1, namely the sum of selenium relative to copper and gallium is excessive. In a preferred scheme, the molar ratio of selenium in the selenium thin film layer to the sum of copper and gallium in the copper-indium-gallium prefabricated layer is 1.6-2.2. More preferably, the molar ratio of selenium in the selenium thin film layer to the sum of copper and gallium in the copper-indium-gallium prefabricated layer is 1.6-1.8.
And S30, placing the copper indium gallium prefabricated layer on which the selenium thin film layer is formed in an annealing furnace.
Compared with the traditional annealing furnace, the annealing furnace provided by the embodiment of the invention is also provided with the gas spraying device in the reaction chamber of the annealing furnace, and the gas spraying device is arranged above the supporting platform for bearing the copper indium gallium prefabricated layer in the annealing furnace.
In step S30, after the copper indium gallium pre-fabricated layer on which the selenium thin film layer is deposited is placed in an annealing furnace, a chamber of the annealing furnace is first subjected to a gas cleaning process and then a vacuum process. Specifically, the performing the scrubbing treatment specifically comprises: and vacuumizing the chamber of the annealing furnace, introducing nitrogen, and repeating the steps for more than 3 times.
S40, heating the copper indium gallium prefabricated layer to a first preset temperature and then keeping the temperature for a first preset time.
The step is mainly to preheat the copper indium gallium prefabricated layer, so that the surface of the copper indium gallium prefabricated layer becomes smoother. In a preferred embodiment, the first predetermined temperature may be set to be in a range of 80 ℃ to 200 ℃, and the first predetermined time may be set to be in a range of 1min to 3 min. Further, the time for heating the copper indium gallium prefabricated layer from the room temperature to the first predetermined temperature is preferably 0.5min to 1 min.
In a preferred scheme, a small amount of hydrogen sulfide gas is also introduced into the annealing furnace within the first preset time, so that the basic concentration of the hydrogen sulfide gas is kept in the reaction process, and the prefabricated layer in the subsequent process is easier to vulcanize. Preferably, a mixed gas of hydrogen sulfide and nitrogen is introduced into the annealing furnace, wherein the gas is introduced at a rate of 0.2sccm/cm2～2sccm/cm2The volume concentration of the hydrogen sulfide is 0.5-3%.
A small amount of hydrogen sulfide gas is also introduced into the annealing furnace within the first preset time, so that on one hand, the basic concentration of the hydrogen sulfide gas can be maintained, and the prefabricated layer in the subsequent process is easier to vulcanize; on the other hand, the mixed gas of hydrogen sulfide and nitrogen is introduced, so that the air pressure in the annealing furnace can be kept stable, and defects caused by pyrolysis on the surface of the prefabricated layer when the air pressure in the furnace is too low are prevented. At this stage, because the concentration of selenium vapor in the furnace is high, when the volume concentration of hydrogen sulfide is about 3%, sulfuration does not occur, and the selenization process is not affected, but if the concentration of hydrogen sulfide is further increased, sulfuration and selenization may occur simultaneously, so that the concentration of the introduced hydrogen sulfide gas in the first predetermined time is kept below 3%.
And S50, heating the copper indium gallium prefabricated layer from the first preset temperature to the second preset temperature, and keeping the temperature for the second preset time to selenize the copper indium gallium prefabricated layer.
In a preferred embodiment, the second predetermined temperature may be set to be in a range of 500 to 600 ℃, and the second predetermined time may be set to be in a range of 0.5 to 3 min. Further, the copper indium gallium prefabricated layer is heated from the first preset temperature to the second preset temperature for preferably 2min to 5 min.
Preheating the prefabricated layer plated with selenium, heating to 500-600 ℃ (preferably 580-600 ℃), and selenizing at the temperature to grow the crystal so as to form the good copper indium gallium selenide crystal. In the embodiment of the invention, as mentioned above, the selenium is excessive, and the selenization is performed by using the excessive selenium, so that the crystallization quality of the copper indium gallium selenide (CIGSe) is improved.
And S60, introducing hydrogen sulfide gas through a spraying device arranged in the annealing furnace, so that the excessive selenium steam in the annealing furnace is discharged and the hydrogen sulfide gas is stored.
Specifically, the gas is passed through the spraying device from above the copper indium gallium pre-manufactured layer after selenization is completed, and pure hydrogen sulfide gas, preferably mixed gas of hydrogen sulfide and nitrogen, may be introduced. When the mixed gas is introduced, the volume concentration of the hydrogen sulfide is 2-20 percent, and the rate of introducing the mixed gas is 0.2sccm/cm2～2sccm/cm2. The mixed gas of hydrogen sulfide and nitrogen is introduced, so that the excess selenium steam can be better discharged, and the excessive hydrogen sulfide amount cannot be caused. At this stage, since selenium vapor is discharged, sulfuration can be achieved using a hydrogen sulfide gas having a small concentration. Because the hydrogen sulfide gas is a toxic gas, the consumption of the hydrogen sulfide gas is reduced as much as possible on the premise of meeting the requirement of sulfuration, and in the preferred scheme, when the mixed gas is introduced, the volume concentration of the hydrogen sulfide is 2-10%, and the more preferred concentration is 2-5%.
Specifically, the distance between the spraying device and the upper surface of the copper indium gallium prefabricating layer is controlled to be approximately 2 mm-3 mm, when gas is introduced, hydrogen sulfide gas (or mixed gas) is uniformly discharged from a small hole array of the spraying device and sprayed to the surface of the copper indium gallium prefabricating layer, and excessive selenium steam on the surface of the copper indium gallium prefabricating layer is pushed to flow to the edge and is discharged from an exhaust hole of the annealing furnace.
In some embodiments, it is also contemplated to evacuate the excess selenium vapor by evacuation. However, due to the fact that the gas content in the reaction chamber is reduced and the gas pressure is reduced in the air pumping process, the surface of the copper indium gallium prefabricated layer after selenization is decomposed at high temperature to form defects and reduce the performance of the device by adopting the vacuum pumping mode. Therefore, the excessive selenium vapor is pumped out in a vacuum pumping mode, generally, the excessive selenium vapor cannot be pumped out completely, and the selenization reaction cannot be completely finished.
According to the invention, the excessive selenium steam is discharged in a way of introducing hydrogen sulfide gas through the spraying device, so that the stable air pressure in the annealing furnace can be kept, the selenium steam can be completely discharged to finish the selenizing reaction, and the influence of the selenium steam on the subsequent sulfurization process can be more effectively avoided.
And S70, keeping the copper indium gallium prefabricated layer at the second preset temperature for a third preset time to enable the copper indium gallium prefabricated layer to be vulcanized, and preparing the copper indium gallium selenide sulfur light absorption layer.
In a preferred embodiment, the third predetermined time may be set to be in a range of 2min to 5 min.
In a preferred scheme, after the temperature is kept to the third preset time, the annealing furnace is naturally cooled to the third preset temperature, then, at the third preset temperature, the chamber of the annealing furnace is vacuumized and then nitrogen protective gas is introduced (the residual reaction gas and some multi-component compounds are prevented from polluting the surface of the sample after being cooled), then, the fourth preset temperature is continuously cooled, and at the fourth preset temperature, the prepared product is taken out of the annealing furnace. The third preset temperature is selected to be within the range of 200-300 ℃, and the fourth preset temperature is selected to be within the range of 70-90 ℃.
Example 1
Firstly, preparing a back electrode: molybdenum with the thickness of 1000nm is evaporated on a soda-lime glass substrate to be used as a back electrode.
Secondly, preparing a copper indium gallium prefabricated layer: and (3) sputtering and depositing a copper-gallium film with the thickness of 200nm on the molybdenum back electrode by using a copper-gallium target with the gallium content of 20-30%, and then continuously sputtering and depositing an indium film with the thickness of 500nm on the sample wafer by using an indium target.
And thirdly, evaporating a solid selenium film layer with the thickness of 700nm on the copper indium gallium prefabricated layer, wherein the molar ratio of selenium in the selenium film layer to the sum of copper and gallium in the copper indium gallium prefabricated layer is 1.6.
Fourthly, placing the copper indium gallium prefabricated layer plated with the selenium into a sealable annealing furnace, and carrying out gas washing in the annealing furnace: vacuumizing, filling nitrogen, repeating the steps for 3 times, and finally keeping the vacuumizing state.
And fifthly, selenizing and vulcanizing the copper indium gallium prefabricated layer step by step to obtain the light absorption layer.
Specifically, referring to fig. 3, preheating is carried out firstly, heating is carried out for 1 minute to 80 ℃, and heat preservation is carried out for 3 minutes; then heating to 590 ℃ after 3 minutes, and preserving the heat for 3 minutes for selenization; after the selenization is finished, introducing mixed gas of hydrogen sulfide and nitrogen (the volume concentration of the hydrogen sulfide is 5%) through a spraying device, on one hand, the mixed gas is used for discharging excessive selenium steam, and on the other hand, hydrogen sulfide gas used in the subsequent sulfuration is introduced; after the air pressure is stable, continuously preserving the heat for 3 minutes at the temperature of 590 ℃ for vulcanization; after the heat preservation is finished, naturally cooling to 260 ℃, vacuumizing the annealing furnace, introducing nitrogen protection gas and then continuously cooling; and when the temperature is reduced to about 80 ℃, taking out the annealing sample.
Sixthly, preparing and forming a cadmium sulfide buffer layer with the thickness of 50nm on the light absorption layer by a chemical water bath method.
And seventhly, preparing an intrinsic zinc oxide layer, a conductive zinc oxide layer and a gate electrode for collecting current in sequence on the cadmium sulfide buffer layer by adopting a traditional process, thereby preparing and obtaining the thin-film solar cell.
Fig. 4 is an I-V graph of the solar cell prepared in this example, which had an open circuit voltage (Voc) of 605mV, a short circuit current (Isc) of 17.8mA, a Fill Factor (FF) of 66.35%, and a conversion efficiency (Eff) of 14.97%.
Fig. 5 is an SEM image of a cross section of the solar cell fabricated in the present example, and it can be understood from fig. 5 that the light absorbing layer of the solar cell fabricated by the above method has a good crystalline state and a uniform thickness.
In the above embodiment, firstly, an excessive amount of selenium is used for selenization to form a good copper indium gallium selenide semiconductor crystal; the mode of letting in hydrogen sulfide gas after the selenization is finished is in order to discharge excessive selenium vapour, can be so that keep stable atmospheric pressure in the annealing furnace, can discharge selenium vapour completely in order to finish the selenization reaction, realizes that selenization and vulcanization separate better, has controlled the reaction competition relation of selenium and sulphur, avoids excessive selenium to cause adverse effect to the vulcanization process. After excessive selenium vapor is completely discharged as far as possible, the activity of sulfur is greatly improved, the sulfur can pass through a crystal boundary, and CIGSSe crystals are formed on the surfaces on the two sides of the light absorption layer, so that the sulfur enters a selenium deficiency vacancy to make up for the defects of the formed CIGS crystals, and meanwhile, the forbidden bandwidth on the surfaces on the two sides of the light absorption layer can be improved under the condition of less influence on the forbidden bandwidth in the light absorption layer, so that good V-shaped gradient distribution is achieved, and the high-quality light absorption layer is obtained.
The foregoing is directed to embodiments of the present application and it is noted that numerous modifications and adaptations may be made by those skilled in the art without departing from the principles of the present application and are intended to be within the scope of the present application.
Claims (7)
1. A method for preparing a light absorption layer of a thin film solar cell is characterized by comprising the following steps:
preparing a copper indium gallium prefabricated layer by applying a magnetron sputtering process;
evaporating and depositing on the copper indium gallium prefabricated layer to form a selenium film layer, wherein the molar ratio of selenium in the selenium film layer to the sum of copper and gallium in the copper indium gallium prefabricated layer is more than 1;
placing the copper indium gallium prefabricated layer on which the selenium thin film layer is formed in an annealing furnace;
heating the copper indium gallium prefabricated layer to a first preset temperature and then keeping the temperature for a first preset time;
heating the copper indium gallium prefabricated layer from the first preset temperature to a second preset temperature, and then keeping the temperature for a second preset time to selenize the copper indium gallium prefabricated layer;
introducing hydrogen sulfide gas from the upper part of the copper indium gallium prefabricated layer after selenization through a spraying device arranged in the annealing furnace, so that excessive selenium steam in the annealing furnace is discharged and the hydrogen sulfide gas is stored;
maintaining the copper indium gallium prefabricated layer at the second preset temperature for a third preset time to enable the copper indium gallium prefabricated layer to be vulcanized, and preparing a copper indium gallium selenide sulfide light absorption layer;
wherein the first preset temperature is 80-200 ℃, and the first preset time is 1-3 min; the second preset temperature is 500-600 ℃, the second preset time is 0.5-3 min, and the third preset time is 2-5 min;
wherein, the mixed gas of hydrogen sulfide and nitrogen is also introduced into the annealing furnace in the first preset time, wherein the gas introduction rate is 0.2sccm/cm2～2sccm/cm2The volume concentration of the hydrogen sulfide is 0.5-3%.
2. The method as claimed in claim 1, wherein the time for heating the copper indium gallium pre-fabricated layer from room temperature to the first predetermined temperature is 0.5min to 1min, and the time for heating the copper indium gallium pre-fabricated layer from the first predetermined temperature to the second predetermined temperature is 3min to 5 min.
3. The method according to claim 1, wherein the gas introduced by the shower device is a mixed gas of hydrogen sulfide and nitrogen, the mixed gas has a hydrogen sulfide volume concentration of 2% to 20%, and the mixed gas is introduced at a rate of 0.2sccm/cm2～2sccm/cm2。
4. The method for producing a light-absorbing layer of a thin-film solar cell according to any one of claims 1 to 3, wherein after the copper indium gallium pre-fabricated layer on which the selenium thin-film layer is deposited is placed in an annealing furnace, a chamber of the annealing furnace is subjected to a gas-washing treatment and then a vacuum-pumping treatment, and then heated to the first predetermined temperature; naturally cooling to a third preset temperature after the heat preservation is finished until the third preset time is finished, then firstly carrying out vacuum-pumping treatment on the chamber of the annealing furnace at the third preset temperature, then introducing nitrogen protective gas until the chamber is cooled to a fourth preset temperature, and taking out the prepared product from the annealing furnace at the fourth preset temperature; wherein the third predetermined temperature is 200-300 ℃, and the fourth predetermined temperature is 70-90 ℃.
5. The method as claimed in claim 1, wherein the Cu-in-Ga prefabricated layer has a Cu-in-Ga sum molar ratio of 0.9-0.95 and a Ga-in-Ga sum molar ratio of 0.1-0.3.
6. The method for preparing the light absorption layer of the thin film solar cell according to claim 1, wherein the molar ratio of the selenium in the selenium thin film layer to the sum of the copper and the gallium in the copper and indium gallium prefabricated layer is 1.6-2.2.
7. The method of claim 1 or 6, wherein the selenium thin film layer has a thickness of 700nm to 1000 nm.
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