CN111416015A - Solar cell and preparation method thereof - Google Patents

Solar cell and preparation method thereof Download PDF

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CN111416015A
CN111416015A CN201811545687.1A CN201811545687A CN111416015A CN 111416015 A CN111416015 A CN 111416015A CN 201811545687 A CN201811545687 A CN 201811545687A CN 111416015 A CN111416015 A CN 111416015A
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zinc oxide
layer
oxide layer
equal
doping concentration
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卢海江
孙红霞
任晓东
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Dongjun new energy Co.,Ltd.
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Lingfan New Energy Technology Beijing Co ltd
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    • H—ELECTRICITY
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    • H01L31/02—Details
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    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H01L31/02168—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells the coatings being antireflective or having enhancing optical properties for the solar cells
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    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
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    • 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
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    • 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
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    • 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
    • H01L31/0323—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 characterised by the doping material
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    • 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
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    • H01L31/0392—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 their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
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    • H01L31/03928—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 their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate comprising a flexible substrate including AIBIIICVI compound, e.g. CIS, CIGS deposited on metal or polymer foils
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    • 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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    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/541—CuInSe2 material PV cells
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    • 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 solar cell and a preparation method thereof, wherein the solar cell comprises an electrode layer, a window layer and a buffer layer, the window layer is arranged between the electrode layer and the buffer layer, the window layer comprises at least three zinc oxide layers, and the aluminum doping concentration in each zinc oxide layer is increased in a gradient manner along the direction of the buffer layer pointing to the electrode layer. According to the technical scheme, the series resistance of the solar cell can be reduced, the optical transmittance of the solar cell is improved, and finally the photoelectric conversion efficiency of the whole solar cell is improved.

Description

Solar cell and preparation method thereof
Technical Field
The invention relates to the technical field of solar energy, in particular to a solar cell and a preparation method thereof.
Background
The window layer of the solar cell is important for fully absorbing sunlight and improving the photoelectric conversion efficiency of the solar cell. In the prior art, part of the window layer of a solar cell is formed by overlapping an intrinsic zinc oxide (i-ZnO) thin film and an aluminum-doped zinc oxide (Al-ZnO) thin film, such as a Copper Indium Gallium Selenide (CIGS) thin film solar cell, a cadmium telluride thin film solar cell, and the like, wherein the intrinsic zinc oxide thin film is a zinc oxide thin film which is not doped or has a very low doping concentration, and the aluminum-doped zinc oxide thin film is a zinc oxide thin film which is doped with aluminum with a certain concentration and is N-type conductive. The intrinsic zinc oxide film mainly has the effect of reducing the leakage current of the battery, the larger the thickness of the intrinsic zinc oxide film layer is, the smaller the leakage current of the battery is, but the resistivity of the intrinsic zinc oxide film layer is higher. When the film thickness of the intrinsic zinc oxide is increased, the series resistance of the battery is larger, and the efficiency of the whole battery is influenced, and by comprehensively considering the two factors, the doping concentration of aluminum in the intrinsic zinc oxide prepared generally is 0.1 wt% (weight ratio), and the film thickness of the intrinsic zinc oxide is 20 nm. The aluminum-doped zinc oxide film is connected with an electrode of a battery, theoretically, higher aluminum doping concentration is needed to obtain lower resistivity, but if the resistivity of the aluminum-doped zinc oxide is too low, the carrier concentration in the aluminum-doped zinc oxide film can be very high and the internal defects can be increased, so that the optical band gap of the aluminum-doped zinc oxide film is reduced, and the carrier can absorb and reflect near infrared light, so that the transmittance of the aluminum-doped zinc oxide film to the near infrared light is reduced, how to balance the resistivity and the optical transmittance of the aluminum-doped zinc oxide film, and how to improve the efficiency of the solar battery is the problem to be solved urgently at present.
Disclosure of Invention
In view of the above, the present invention is directed to a solar cell and a method for manufacturing the same, which can improve the conversion efficiency of the solar cell.
The solar cell provided by the invention based on the above purpose comprises an electrode layer, a window layer and a buffer layer, wherein the window layer is arranged between the electrode layer and the buffer layer, the window layer comprises at least three zinc oxide layers, and the aluminum doping concentration in each zinc oxide layer increases in a gradient manner along the direction of the buffer layer pointing to the electrode layer.
Further, in the at least three zinc oxide layers: the zinc oxide layer adjacent to the electrode layer is a first zinc oxide layer, the zinc oxide layer adjacent to the buffer layer is a second zinc oxide layer, and the zinc oxide layer between the first zinc oxide layer and the second zinc oxide layer is a middle zinc oxide layer, wherein: the aluminum doping concentration of the first zinc oxide layer is more than or equal to 3.0 wt% and less than or equal to 4.5 wt%; the aluminum doping concentration of the second zinc oxide layer is more than or equal to 0 wt% and less than or equal to 0.05 wt%.
Further, the aluminum doping concentration of the intermediate zinc oxide layer is more than 0 wt% and less than 4.5 wt%.
Furthermore, the thicknesses of the first zinc oxide layer and the second zinc oxide layer are both greater than or equal to 5nm and less than or equal to 10 nm.
Further, in the at least three zinc oxide layers: the total thickness of the first zinc oxide layer is more than or equal to 20nm and less than or equal to 50nm, the total thickness of the second zinc oxide layer is more than or equal to 200nm, and the total thickness of the third zinc oxide layer is more than or equal to 10nm and less than or equal to 80 nm; wherein: the first type zinc oxide layer is a zinc oxide layer with aluminum doping concentration of more than or equal to 0 wt% and less than or equal to 0.5 wt%, the second type zinc oxide layer is a zinc oxide layer with aluminum doping concentration of more than or equal to 1.0 wt% and less than or equal to 2.5 wt%, and the third type zinc oxide layer is a zinc oxide layer with aluminum doping concentration of more than or equal to 3.0 wt% and less than or equal to 4.5 wt%.
Further, the thickness of the window layer is greater than or equal to 300nm and less than or equal to 450 nm.
Furthermore, the solar cell also comprises a light absorption layer, a back electrode layer and a substrate which are arranged on one side of the buffer layer, which is far away from the window layer.
The invention also provides a preparation method of the solar cell, which comprises the following steps:
providing a substrate with a buffer layer;
forming a window layer on the buffer layer;
and forming an electrode layer on the window layer, wherein the formed window layer comprises at least three zinc oxide layers, and the doping concentration of aluminum in each zinc oxide layer is increased in a gradient manner along the direction of the buffer layer pointing to the electrode layer.
Further, the forming of the window layer on the buffer specifically includes: forming each zinc oxide layer by using a magnetron sputtering method; the zinc oxide layer with the corresponding aluminum doping concentration is prepared by controlling the aluminum doping concentration of the target corresponding to each zinc oxide layer, and the zinc oxide layer with the corresponding thickness is formed by controlling the power of the target corresponding to each zinc oxide layer.
Further, the at least three zinc oxide layers are formed by: the zinc oxide layer adjacent to the electrode layer is a first zinc oxide layer, the zinc oxide layer adjacent to the buffer layer is a second zinc oxide layer, and the zinc oxide layer between the first zinc oxide layer and the second zinc oxide layer is a middle zinc oxide layer, wherein: the aluminum doping concentration of the first zinc oxide layer is greater than or equal to 3.0 wt% and less than or equal to 4.5 wt%; the aluminum doping concentration of the formed second zinc oxide layer is more than or equal to 0 wt% and less than or equal to 0.05 wt%.
From the above, according to the solar cell and the preparation method thereof provided by the invention, the plurality of zinc oxide layers with different aluminum doping concentrations are arranged, so that the band gap difference between the zinc oxide layers with different concentrations in the window layer is reduced, electrons can be transferred between the layers more conveniently, and the electron mobility of the electrons in the whole window layer can be further improved.
According to the solar cell and the preparation method thereof provided by the invention, the aluminum doping concentration of the zinc oxide layer on the electrode layer side is improved by arranging the zinc oxide layers with different doping concentrations, the resistivity of the electrode layer side is effectively reduced, and the doping concentration is reduced in a gradient manner along the direction of the electrode layer to the buffer layer, so that the carrier concentration in the whole window layer can be reduced, the absorption and reflection of the window layer to near infrared light can be effectively avoided, and the light transmittance of the window layer is improved. Compared with the intrinsic zinc oxide in the prior art in which the doping concentration of aluminum is 0.1 wt%, the aluminum doping concentration of the zinc oxide layer on the buffer layer side in the technical scheme is lower, so that the injection of aluminum atoms into the buffer layer and the absorption layer is effectively reduced, the interface state density is reduced, the requirement of controlling the leakage current of the battery can be met in a smaller thickness, the series resistance of the battery is reduced, and the performance of the battery is further effectively improved.
Drawings
Fig. 1 is a schematic structural diagram of a solar cell according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for manufacturing a solar cell according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are used for distinguishing two entities with the same name but different names or different parameters, and it should be noted that "first" and "second" are merely for convenience of description and should not be construed as limitations of the embodiments of the present invention, and they are not described in any more detail in the following embodiments.
As shown in fig. 1, the solar cell provided by the present invention includes an electrode layer 109, a window layer 108 and a buffer layer 107, wherein the window layer 108 is disposed between the electrode layer 109 and the buffer layer 107, the window layer 108 includes at least three zinc oxide layers, and the doping concentration of aluminum in each zinc oxide layer increases in a gradient manner along a direction (refer to a direction indicated by a solid arrow in fig. 1) in which the buffer layer points to the electrode layer.
Compared with the window layer formed by overlapping intrinsic zinc oxide and single-concentration aluminum-doped zinc oxide in the prior art, the window layer at least comprises three zinc oxide layers, and by arranging a plurality of zinc oxide layers with different aluminum doping concentrations, the band gap difference between the zinc oxide layers with different concentrations in the window layer is reduced, electrons can conveniently migrate between the layers, and the electron mobility of the electrons in the whole window layer can be further improved.
Wherein the buffer layer 107 is typically a cadmium sulfide layer, a zinc sulfide layer, or a zinc oxy sulfide layer. Optionally, the thickness of the buffer layer 107 is greater than or equal to 40nm and less than or equal to 60 nm. Optionally, the buffer layer has a thickness of 40nm, 45nm, 47nm, 52nm, 56nm, or 60 nm.
Wherein, the electrode layer 109 is selected from a silver electrode or a nickel aluminum electrode.
In some embodiments of the invention, the at least three zinc oxide layers comprise: the zinc oxide layer adjacent to the electrode layer is a first zinc oxide layer, the zinc oxide layer adjacent to the buffer layer is a second zinc oxide layer, and the zinc oxide layer between the first zinc oxide layer and the second zinc oxide layer is a middle zinc oxide layer, wherein: the aluminum doping concentration of the first zinc oxide layer is more than or equal to 3.0 wt% and less than or equal to 4.5 wt%; the aluminum doping concentration of the second zinc oxide layer is more than or equal to 0 wt% and less than or equal to 0.05 wt%. In the prior art, the maximum doping concentration of the aluminum-doped zinc oxide film is only 3 wt%, and the requirement of an electrode layer on low resistivity cannot be met, the technical scheme is that a plurality of zinc oxide layers with different doping concentrations are arranged, so that the aluminum doping concentration in the zinc oxide layer close to the electrode layer side is improved, the resistivity of the electrode layer side is effectively reduced, and the doping concentration is reduced in a gradient manner along the direction from the electrode layer to a buffer layer (refer to the direction shown by a dotted arrow in fig. 1), so that the carrier concentration in the whole window layer can be reduced, the absorption and reflection of the window layer on Near Infrared light are effectively avoided, the light transmittance of the window layer is improved, wherein the Near Infrared light (NIR) is electromagnetic wave between visible light (vis) and mid Infrared light (MIR). Compared with the prior art in which the doping concentration of aluminum in intrinsic zinc oxide is 0.1 wt%, the aluminum doping concentration of the zinc oxide layer on the buffer layer side in the technical scheme is lower, so that the injection of aluminum atoms into the buffer layer and the absorption layer is effectively reduced, the interface state density is reduced, the requirement of controlling the leakage current of the battery can be met in a smaller thickness, the series resistance of the battery is reduced, and the performance of the battery is further effectively improved.
In some embodiments of the invention, the intermediate zinc oxide layer has an aluminum doping concentration greater than 0 wt% and less than 4.5 wt%. For example, when the aluminum doping concentration of the first zinc oxide layer is 4.5 wt% and the aluminum doping concentration of the second zinc oxide layer is 0 wt%, the aluminum doping concentration of the intermediate zinc oxide layer may be 0.05 wt%, 0.5 wt%, 0.8 wt%, 1.2 wt%, 1.8 wt%, 2.0 wt%, 2.5 wt%, 3.5 wt%, 3.8 wt%, 4.1 wt%, 4.2 wt%, 4.4 wt%, and the like, in this order. For example, when the aluminum doping concentration of the first zinc oxide layer is 4.0 wt% and the aluminum doping concentration of the second zinc oxide layer is 0.03 wt%, the aluminum doping concentration of the intermediate zinc oxide layer may be 0.04 wt%, 0.7 wt%, 1.5 wt%, 2.1 wt%, 2.4 wt%, 3.5 wt%, 3.8 wt%, and the like, in this order. For example, when the aluminum doping concentration of the first zinc oxide layer is 3.5 wt% and the aluminum doping concentration of the second zinc oxide layer is 0.05 wt%, the aluminum doping concentration of the intermediate zinc oxide layer may be 0.1 wt%, 0.5 wt%, 1.0 wt%, 1.4 wt%, 2.2 wt%, 3.0 wt%, 3.2 wt%, and the like, in this order.
In some embodiments of the present invention, the thickness of each of the first zinc oxide layer and the second zinc oxide layer is greater than or equal to 5nm and less than or equal to 10nm, for example, 5nm, 6nm, 7nm, 8nm, 9.5nm, 10nm, etc., which are not listed here. . The technical scheme of the invention limits the thickness of the zinc oxide layer adjacent to the electrode layer, can ensure that the overall carrier concentration of the window layer is not increased while the low resistivity and the electrons are effectively collected and transmitted, limits the thickness of the zinc oxide layer adjacent to the buffer layer, can effectively avoid the increase of the resistivity caused by the increase of the thickness, ensures that the leakage current of the battery is reduced while the overall resistivity of the window layer is not increased, and improves the light energy conversion efficiency of the battery.
In some embodiments of the invention, the at least three zinc oxide layers comprise: the total thickness of the first zinc oxide layer is more than or equal to 20nm and less than or equal to 50nm, the total thickness of the second zinc oxide layer is more than or equal to 200nm, and the total thickness of the third zinc oxide layer is more than or equal to 10nm and less than or equal to 80 nm; wherein: the first type zinc oxide layer is a zinc oxide layer with aluminum doping concentration of more than or equal to 0 wt% and less than or equal to 0.5 wt%, the second type zinc oxide layer is a zinc oxide layer with aluminum doping concentration of more than or equal to 1.0 wt% and less than or equal to 2.5 wt%, and the third type zinc oxide layer is a zinc oxide layer with aluminum doping concentration of more than or equal to 3.0 wt% and less than or equal to 4.5 wt%. The thickness of the zinc oxide layers in different aluminum doping concentration ranges is non-uniformly distributed, the thickness of the zinc oxide layer with low aluminum doping concentration and the thickness of the zinc oxide layer with high aluminum doping concentration are small, the thickness of the zinc oxide layer with middle doping concentration is large, the zinc oxide layer with low aluminum doping concentration is prevented from increasing the series resistance of the cell, the absorption and reflection of near infrared light caused by overhigh carrier concentration due to high doping concentration are avoided, and therefore lower resistivity and higher optical transmittance are guaranteed. Specifically, the following are exemplified: three zinc oxide layers in the window layer belong to the first type of zinc oxide layer, the three corresponding aluminum doping concentrations and thicknesses of the zinc oxide layer with the aluminum doping concentration of 0 wt% and the zinc oxide layer with the aluminum doping concentration of 0.2 wt% and the zinc oxide layer with the aluminum doping concentration of 0.5 wt% are sequentially 5nm thick, 5nm thick and 15nm thick, and the total thickness of the three zinc oxide layers is 25 nm; four zinc oxide layers in the window layer belong to the second zinc oxide layer, the aluminum doping concentration and the thickness of the four zinc oxide layers are respectively a zinc oxide layer with the aluminum doping concentration of 1.0 wt% and the aluminum doping concentration of 40nm thick, a zinc oxide layer with the aluminum doping concentration of 1.8 wt% and the aluminum doping concentration of 60nm thick, a zinc oxide layer with the aluminum doping concentration of 2.0 wt% and the aluminum doping concentration of 2.3 wt% and the total thickness of the four zinc oxide layers is 300 nm; two zinc oxide layers in the window layer belong to the third type of zinc oxide layer, the aluminum doping concentration and the thickness of the two zinc oxide layers are respectively a zinc oxide layer with the aluminum doping concentration of 3.1 wt% and a zinc oxide layer with the aluminum doping concentration of 4.2 wt% and the thickness of 20nm, and the total thickness of the two zinc oxide layers is 30 nm.
In some embodiments of the invention, the aluminum-doped zinc oxide thin film has a thickness of 300nm to 450 nm. Those skilled in the art will understand that the thickness of the aluminum-doped zinc oxide film can be flexibly set according to actual requirements, for example, 300nm, 350nm, 400nm, 420nm, 450nm, etc.
In some embodiments of the present invention, the solar cell further comprises a light absorbing layer 106, a back electrode layer and a substrate 101 disposed on a side of the buffer layer 107 facing away from the window layer 108. Optionally, the light absorbing layer 106 is a CIGS absorbing layer, the CIGS absorbing layer is a P-type semiconductor, the buffer layer is an N-type semiconductor, and the CIGS absorbing layer and the buffer layer 107 can form a PN junction to form the most core structure of the solar cell. Wherein the substrate mainly supports the solar cell, and the substrate can be selected from the following materials: stainless steel, glass or high molecular weight polymers. The type and the characteristics of the substrate determine the mechanical performance and the application scene of the solar cell; specifically, solar cells fabricated on rigid glass or stainless steel substrates are generally used in roofs, power stations, and walls, and solar cells fabricated on flexible high molecular polymers can be used in wearable devices.
In some embodiments of the present invention, the back electrode layer comprises a second molybdenum layer 105, a molybdenum sodium layer 104 and a first molybdenum layer 103, which are sequentially disposed on the light absorbing layer 106 side facing away from the buffer layer 107. Optionally, when the substrate is made of stainless steel, a titanium layer is further disposed on a side of the first molybdenum layer close to the substrate. The titanium layer 102 and the first molybdenum layer 103 are both a barrier layer and a back electrode of the battery and play a role of double-layer barrier, sodium atoms in the molybdenum sodium layer 104 contribute to growth of the copper indium gallium selenide layer and can improve the performance of the battery, and the second molybdenum layer 105 contributes to forming good ohmic contact with the light absorption layer 106, so that the series resistance of the whole battery is reduced, and the adhesion force between film layers can be increased. Optionally, the thickness of the titanium layer is greater than or equal to 300nm and less than or equal to 500nm, such as 320nm, 350nm, 400nm, or 480 nm. Optionally, the thickness of the first molybdenum layer is greater than or equal to 150nm and less than or equal to 300nm, such as 180nm, 240nm, or 268 nm. Optionally, the thickness of the molybdenum sodium layer is greater than or equal to 150nm and less than or equal to 300nm, such as 170nm, 200nm, or 250 nm. Optionally, the thickness of the second molybdenum layer is greater than or equal to 10nm and less than or equal to 20nm, such as 12nm, 16nm, or 18 nm.
As shown in fig. 2, the present invention also provides a method for manufacturing a solar cell, the method comprising: step 201: providing a substrate with a buffer layer; step 202: forming a window layer on the buffer layer; step 203: and forming an electrode layer on the window layer, wherein the formed window layer comprises at least three zinc oxide layers, and the doping concentration of aluminum in each zinc oxide layer is increased in a gradient manner along the direction of the buffer layer pointing to the electrode layer.
In some embodiments of the inventionIn an embodiment, the step 202 of forming a window layer on the buffer specifically includes: forming each zinc oxide layer by using a magnetron sputtering method; the zinc oxide layer with the corresponding aluminum doping concentration is prepared by controlling the aluminum doping concentration of the target corresponding to each zinc oxide layer, and the zinc oxide layer with the corresponding thickness is formed by controlling the power of the target corresponding to each zinc oxide layer. Wherein the target material comprises Al2O3And ZnO by adjusting Al2O3The weight percentage (wt%) in the target material realizes the control of the doping concentration of each target material.
In the magnetron sputtering equipment, N targets are preset along the movement direction of a substrate with a buffer layer deposited in the magnetron sputtering equipment, the aluminum doping concentration gradient of the N targets is increased, the number of the targets is equal to the number of zinc oxide layers set by a window layer, the doping concentration of the nth target is adaptive to the aluminum doping concentration set by the nth zinc oxide layer along the direction from the buffer layer to an electrode layer, wherein N is more than or equal to 3, and N is more than or equal to 1 and less than or equal to N. In the preparation process, the substrate on which the buffer layer is deposited is enabled to sequentially pass through the N targets, and the window layer with the doping concentration gradient change can be prepared. In the preparation process of the aluminum-doped zinc oxide layer, the power of the target directly influences the thickness of the film, the larger the power of the target is, the larger the thickness of the film formed by the target is, and therefore, the control of the layer thickness of the doping concentration is realized by setting the power of each target.
In some embodiments of the present invention, further comprising the step of sequentially depositing a back electrode layer and a light absorbing layer on the substrate.
Example 1
As shown in fig. 1, the present embodiment provides a copper indium gallium selenide thin-film solar cell, which includes a substrate 101 (made of stainless steel material), a titanium layer 102, a first molybdenum layer 103, a molybdenum sodium layer 104, a second molybdenum layer 105, an absorption layer 106(CIGS), a buffer layer 107(CdS), a window layer 108 (made of aluminum gradient doped zinc oxide thin-film layer), and an electrode layer 109 (made of silver material) that are sequentially disposed; the window layer 108 includes 12 zinc oxide layers with different aluminum doping concentrations, each doping concentration and corresponding thickness are detailed in table 1, and the window layer is prepared by the following method:
performing continuous film deposition on a stainless steel substrate 101 by adopting a magnetron sputtering method, wherein the thickness of the stainless steel substrate is 50um, the width of the stainless steel substrate is 0.5m, and the vacuum of a coating chamber is 1 × 10-5Torr；
Depositing a first metal Ti film on a substrate to form a titanium layer 102 at room temperature, wherein the thickness of the Ti film is 400nm and is used as a barrier layer and a back electrode of a battery;
depositing a second film Mo on the titanium layer 102 to form a first molybdenum layer 103 at room temperature, wherein the thickness of the Mo film is 200nm and is used as a barrier layer and a back electrode of the battery;
depositing a third layer of film MoNa on the Mo film layer to form a molybdenum sodium layer 104 at room temperature, wherein a Mo target doped with 2 wt% of Na atoms is adopted, and the thickness of the MoNa film is 200 nm;
depositing a fourth layer of thin film metal Mo thin film on the MoNa film layer at room temperature, wherein the thickness of the Mo thin film is 15nm corresponding to the second molybdenum layer 105;
and depositing a fifth CIGS film as a CIGS absorption layer 106 on the second molybdenum layer 105, wherein the substrate temperature is 700 ℃, the thickness of the CIGS film is 1.5 mu m, the CIGS crystal grain diameter is 1-1.5 mu m, and the optical band gap is 1.15 ev.
And depositing a sixth CdS film layer on the CIGS thin film layer by adopting a magnetron sputtering method at room temperature, wherein the thickness of the CdS film is 50nm, and the CdS film forms a CdS buffer layer 107.
Depositing a seventh film on the Cds film layer, wherein the aluminum gradient doped zinc oxide film layer is used as a window layer 108 of the CIGS cell, the thickness of the film is 400nm, and the distribution of aluminum impurity gradient doping is shown in Table 1; the gradient doping of the window layer is realized by controlling the doping concentration of each target material, and the thickness of each zinc oxide layer is controlled by controlling the power of each target material;
preparing an electrode layer 109 on the window layer by adopting a magnetron sputtering method at room temperature so as to lead out current;
the large battery is cut into small battery pieces of 300mm × 43mm by adopting a mechanical cutting mode.
TABLE 1 Al doping concentration and thickness parameter table for ZnO layer in EXAMPLE 1
Figure BDA0001909273760000081
Example 2
This example differs from example 1 in that the window layer comprises 6 zinc oxide layers of different doping concentrations of aluminum, each doping concentration and corresponding thickness being specified in table 2.
TABLE 2 Al doping concentration and thickness parameter table for ZnO layer in EXAMPLE 2
Figure BDA0001909273760000082
Figure BDA0001909273760000091
Example 3
This example differs from example 1 in that the window layer comprises 3 zinc oxide layers of different doping concentrations of aluminum, each doping concentration and corresponding thickness being specified in table 3.
TABLE 3 Al doping concentration and thickness parameter table for ZnO layer in EXAMPLE 3
Figure BDA0001909273760000092
It can be understood by those skilled in the art that when the window layer includes only the intrinsic zinc oxide thin film with a doping concentration of 0 wt% and the zinc oxide thin film with an aluminum doping concentration of 4.5 wt%, the solar cell prepared has low efficiency or even fails to convert light energy into electric energy because: 1) if the thickness of the intrinsic zinc oxide is too large, the series resistance of the battery is greatly improved; 2) if the thickness of the zinc oxide film with the doping concentration of 4.5 wt% is too large, the light transmittance of the window layer is greatly reduced, the recombination of photo-generated carriers is increased, the electron transfer efficiency is reduced, and the electron collection efficiency is reduced. Therefore, to further prove the technical effects of the present invention, comparative example 1 and comparative example 2 shown below were provided as comparative examples in which the window layer includes only the intrinsic zinc oxide thin film and the aluminum-doped zinc oxide thin film, with the total thickness of the window layer being constant.
Comparative example 1
Comparative example 1 is different from example 1 in that the window layer of the copper indium gallium selenide solar cell in the present comparative example is composed of a 20nm intrinsic zinc oxide thin film and a 380nm aluminum-doped zinc oxide thin film in which the doping concentration is 3%. Wherein, the zinc oxide film contacts with the CdS buffer layer, and the aluminum-doped zinc oxide film contacts with the silver electrode layer.
Comparative example 2
Comparative example 2 is different from example 1 in that the window layer of the copper indium gallium selenide solar cell in the present comparative example is composed of a 20nm intrinsic zinc oxide thin film and a 380nm aluminum-doped zinc oxide thin film in which the doping concentration is 2%. Wherein, the zinc oxide film contacts with the CdS buffer layer, and the aluminum-doped zinc oxide film contacts with the silver electrode layer.
The 100 batteries prepared in examples 1 to 3 and comparative examples 1 and 2 were respectively tested for battery performance, as detailed in table 4, under the following conditions: at AM1.5 (the actual distance of the light through the atmosphere is 1.5 times the vertical thickness of the atmosphere), the light intensity is 100mw/cm2Standard conditions at 25 degrees celsius.
TABLE 4 Battery Performance test results
Figure BDA0001909273760000101
As can be seen from the results of the cell performance test in table 4, when the number of layers of the zinc oxide layer having different aluminum doping concentrations is larger, that is, the doping concentration of the zinc oxide layer is more uniformly distributed in the range of 0% to 4.5%, the performance of the prepared solar cell is better. The solar cells prepared in examples 1 to 3 have better performance than the solar cells having only two zinc oxide layers with different aluminum doping concentrations in comparative examples 1 and 2, and therefore at least three zinc oxide layers with different aluminum doping concentrations are provided as window layers, and the aluminum doping concentration in each zinc oxide layer increases in a gradient manner along the direction (the direction indicated by the solid arrow in fig. 1) in which the buffer layer points to the electrode layer, so that the difference in the aluminum doping concentration between the zinc oxide layers can be reduced, the aluminum doping concentration between the zinc oxide layers changes more smoothly, and the electron transfer rate in the window layers is increased. In addition, the carrier concentration of the window layer is reduced on the whole, the absorption of red light is reduced, and the optical transmittance is increased. The aluminum doping concentration of the window layer on the electrode layer side is increased, so that the resistivity of the zinc oxide layer on the electrode layer side can be reduced, and electrons can be effectively collected and transmitted; the aluminum doping concentration of the zinc oxide layer on the buffer layer side is reduced, so that the injection of aluminum atoms into the buffer layer and the CIGS absorption layer can be blocked at a very low thickness, the leakage current of the cell is effectively reduced, the series resistance of the solar cell is reduced, and the photoelectric conversion efficiency of the whole solar cell is finally improved.
Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, is limited to these examples; within the idea of the invention, also features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.
While the present invention has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description.
The embodiments of the invention are intended to embrace all such alternatives, modifications and variances that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, substitutions, improvements and the like that may be made without departing from the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (10)

1. A solar cell comprises an electrode layer, a window layer and a buffer layer, and is characterized in that the window layer is arranged between the electrode layer and the buffer layer, the window layer comprises at least three zinc oxide layers, the buffer layer points to the direction of the electrode layer, and the doping concentration of aluminum in each zinc oxide layer is increased in a gradient manner.
2. The solar cell of claim 1, wherein the at least three zinc oxide layers: the zinc oxide layer adjacent to the electrode layer is a first zinc oxide layer, the zinc oxide layer adjacent to the buffer layer is a second zinc oxide layer, and the zinc oxide layer between the first zinc oxide layer and the second zinc oxide layer is a middle zinc oxide layer, wherein: the aluminum doping concentration of the first zinc oxide layer is more than or equal to 3.0 wt% and less than or equal to 4.5 wt%; the aluminum doping concentration of the second zinc oxide layer is more than or equal to 0 wt% and less than or equal to 0.05 wt%.
3. The solar cell of claim 2, wherein the intermediate zinc oxide layer has an aluminum doping concentration greater than 0 wt% and less than 4.5 wt%.
4. The solar cell of claim 1, wherein the first zinc oxide layer and the second zinc oxide layer each have a thickness of 5nm or more and 10nm or less.
5. The solar cell of claim 1, wherein the at least three zinc oxide layers: the total thickness of the first zinc oxide layer is more than or equal to 20nm and less than or equal to 50nm, the total thickness of the second zinc oxide layer is more than or equal to 200nm, and the total thickness of the third zinc oxide layer is more than or equal to 10nm and less than or equal to 80 nm; wherein: the first type zinc oxide layer is a zinc oxide layer with aluminum doping concentration of more than or equal to 0 wt% and less than or equal to 0.5 wt%, the second type zinc oxide layer is a zinc oxide layer with aluminum doping concentration of more than or equal to 1.0 wt% and less than or equal to 2.5 wt%, and the third type zinc oxide layer is a zinc oxide layer with aluminum doping concentration of more than or equal to 3.0 wt% and less than or equal to 4.5 wt%.
6. The solar cell of claim 1, wherein the window layer has a thickness of 300nm or more and 450nm or less.
7. The solar cell according to any one of claims 1 to 6, further comprising a light absorbing layer, a back electrode layer and a substrate disposed on a side of the buffer layer facing away from the window layer.
8. A method of fabricating a solar cell, the method comprising:
providing a substrate with a buffer layer;
forming a window layer on the buffer layer;
and forming an electrode layer on the window layer, wherein the formed window layer comprises at least three zinc oxide layers, and the doping concentration of aluminum in each zinc oxide layer is increased in a gradient manner along the direction of the buffer layer pointing to the electrode layer.
9. The method according to claim 8, wherein the forming a window layer on the buffer specifically comprises: forming each zinc oxide layer by using a magnetron sputtering method; the zinc oxide layer with the corresponding aluminum doping concentration is prepared by controlling the aluminum doping concentration of the target corresponding to each zinc oxide layer, and the zinc oxide layer with the corresponding thickness is formed by controlling the power of the target corresponding to each zinc oxide layer.
10. The production method according to claim 9, wherein the at least three zinc oxide layers are formed such that: the zinc oxide layer adjacent to the electrode layer is a first zinc oxide layer, the zinc oxide layer adjacent to the buffer layer is a second zinc oxide layer, and the zinc oxide layer between the first zinc oxide layer and the second zinc oxide layer is a middle zinc oxide layer, wherein: the aluminum doping concentration of the first zinc oxide layer is greater than or equal to 3.0 wt% and less than or equal to 4.5 wt%; the aluminum doping concentration of the formed second zinc oxide layer is more than or equal to 0 wt% and less than or equal to 0.05 wt%.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112054071A (en) * 2020-08-07 2020-12-08 宣城开盛新能源科技有限公司 CIGS flexible thin-film solar cell and preparation method thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112054071A (en) * 2020-08-07 2020-12-08 宣城开盛新能源科技有限公司 CIGS flexible thin-film solar cell and preparation method thereof

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