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WO2025050323A1 - Method for manufacturing a cdte based thin film solar cell device comprising a doped back contact and such a cdte based thin film solar cell device - Google Patents

Method for manufacturing a cdte based thin film solar cell device comprising a doped back contact and such a cdte based thin film solar cell device Download PDF

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Publication number
WO2025050323A1
WO2025050323A1 PCT/CN2023/117327 CN2023117327W WO2025050323A1 WO 2025050323 A1 WO2025050323 A1 WO 2025050323A1 CN 2023117327 W CN2023117327 W CN 2023117327W WO 2025050323 A1 WO2025050323 A1 WO 2025050323A1
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WIPO (PCT)
Prior art keywords
back contact
layer
contact layer
cdte based
cdte
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PCT/CN2023/117327
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French (fr)
Inventor
Shou PENG
Xinjian Yin
Ganhua FU
Liyun MA
Robert Arndt
Somaye BEYZAVI
Bastian SIEPCHEN
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China Triumph International Engineering Co Ltd
CTF Solar GmbH
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China Triumph International Engineering Co Ltd
CTF Solar GmbH
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Priority to PCT/CN2023/117327 priority Critical patent/WO2025050323A1/en
Publication of WO2025050323A1 publication Critical patent/WO2025050323A1/en
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
    • H10F10/16—Photovoltaic cells having only PN heterojunction potential barriers
    • H10F10/162—Photovoltaic cells having only PN heterojunction potential barriers comprising only Group II-VI materials, e.g. CdS/CdTe photovoltaic cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F71/00—Manufacture or treatment of devices covered by this subclass
    • H10F71/125—The active layers comprising only Group II-VI materials, e.g. CdS, ZnS or CdTe
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/12—Active materials
    • H10F77/123—Active materials comprising only Group II-VI materials, e.g. CdS, ZnS or HgCdTe
    • 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

Definitions

  • the invention concerns a CdTe based thin film solar cell device comprising a doped back contact, wherein the back contact is copper-free, and a method for forming such a CdTe based thin film solar cell device.
  • a CdTe based thin film solar cell device is a solar cell device comprising a CdTe based thin film as a photoactive layer also called an absorber layer.
  • a back contact different materials are known.
  • Hall et. al. describes in “Back contacts materials used in thin film CdTe solar cells–A review” , Energy Sci Eng. 2021 (9) that a layer stack comprising a ZnTe layer at the interface to the CdTe based absorber layer and a metal layer on the ZnTe layer is a proper back contact.
  • the ZnTe layer may be doped, for instance with copper. Copper as doping element has some advantages, like reducing the Shottky barrier between the absorber layer and the back contact.
  • the ZnTe layer as a doped layer during deposition, i.e. during spin-coating or sputtering, causes problems with respect to the control of the amount of the doping element and with respect to the process conditions during deposition of the ZnTe layer.
  • Object of the invention is to provide an alternative method for manufacturing a CdTe based thin film solar cell device comprising a copper-free doped back contact and, in the result, a CdTe based thin film solar cell device with improved photovoltaic efficiency and long-term stability.
  • a method for manufacturing a CdTe based thin film solar cell device having a copper-free doped back contact at least comprises the following steps:
  • a semi-finished solar cell device comprising at least a substrate, a front electrode and a CdTe based absorber layer
  • step c) is performed after step b) and directly before or after step d) , wherein no thermal treatment step is performed between step c) and d) if step c) is performed before step d) , and wherein the thermal treatment in step f) is performed after steps c) and d) at a temperature in the range of 230°C to 270°C.
  • this method enables manufacturing a CdTe based thin film solar cell device having a copper-free doped back contact by ex-situ doping.
  • asubstrate means any basis the front electrode and the CdTe based absorber layer is formed onto in the semi-finished solar cell device provided in step a) .
  • the substrate may comprise a transparent base substrate, for instance of glass or polymeric material.
  • the front electrode may be a transparent front electrode, for instance made of a transparent conductive oxide.
  • the semi-finished solar cell device may comprise further layers like buffer layers, window layers, antireflective layers or any else, wherein the further layers may be formed between the substrate and the front electrode or between the front electrode and the CdTe based absorber layer.
  • a CdTe based absorber layer means a layer or layer stack comprising at least one layer of the composition CdTe, Cd 1-x Hg x Te, Cd 1-x Mn x Te, Cd 1-x Mg x Te or CdSe x Te 1-x with x varying between 0 ⁇ x ⁇ 0.5.
  • the layer stack may comprise further layers, for instance one or more CdSe layers.
  • the individual layers of such a layer stack may be formed, for instance, by subsequently depositing one or a plurality of layers, for instance layers of CdSe and CdTe, followed by interdiffusion of the different layers if desired, or in one undivided process.
  • the CdTe based absorber layer is formed as a doped CdTe based absorber layer, doped with any suitable element known from state of the art, wherein advantageously copper is excluded.
  • a doped CdTe based absorber layer may be achieved by any known method, for instance by comprising one or more doping source layers into the CdTe based absorber layer stack or by depositing a doped CdTe based absorber layer using co-deposition of a CdTe based material and at least one doping material.
  • the CdTe based absorber layer is doped with a group 15 element, preferably with P, As, Sb or Bi, or a group 5 element, for instance V.
  • the CdTe based absorber layer may be formed using any technique known from the prior art, comprising, but not limited to, physical vapour deposition, e.g. sputtering, evaporation or sublimation, electrodeposition, or any else.
  • the CdTe based absorber layer is deposited with a thickness from 1 ⁇ m to 5 ⁇ m, preferably with a thickness from 2 ⁇ m to 4 ⁇ m.
  • the activation treatment in step b) results in a CdTe based absorber layer with passivated grain boundaries and saturated defects.
  • the activation treatment in step b) comprises applying an activation agent which is a chlorine comprising material, like for instance CdCl 2 , to a surface of the CdTe based absorber layer and performing a thermal treatment at a temperature in the range of 380°C to 480°C.
  • the activation agent may be applied by wet chemical methods or by vacuum evaporation.
  • the thermal treatment, also called annealing may be performed in air atmosphere for a duration in the range of 5 minutes to 30 minutes.
  • acleaning step may be performed in order to remove residues of the activation agent from the surface of the CdTe based absorber layer.
  • Step b) is always performed after step a) and before step c) .
  • step c) the X-halogen is applied, wherein this step may be performed directly before or after depositing the first back contact layer comprising ZnTe, i.e. directly before or after step d) .
  • step c) is performed before step d)
  • the X-halogen is applied to the surface of the activated CdTe based absorber layer. Due to the activation treatment performed before, the element X or the X-halogen does not diffuse into the CdTe based absorber layer, but diffuses instead into the first back contact layer comprising ZnTe which is deposited afterwards.
  • step c) is performed after step d) , the X-halogen is applied to a surface of the first back contact layer.
  • step c) is performed before step d)
  • the X-halogen is applied in liquid form in step c)
  • the X-halogen may be applied also in gaseous form in step c)
  • Examples for X-halogens, wherein X is selected out of a group consisting of P, As, Sb, Bi and V are but not limiting PCl 3 , AsCl 3 , SbCl 3 , BiCl 3 , VF 5 , VCl 4 , VCl 3
  • AX-halogen in liquid form means a X-halogen present as liquid phase, a X-halogen solution, a X-halogen suspension or a gel-like X-halogen.
  • a X-halogen present as liquid phase is for instance PCl 3 , AsCl 3 , VF 5 , VCl 4 , which are present as liquid phase at room temperature.
  • a X-halogen solution means an X-halogen dissolved in a solvent.
  • the solvent is thereby suitable for solving the X-halogen.
  • Asuitable solvent for VF 5 is for instance water
  • asuitable solvent for AsCl 3 and PCl 3 is for instance ether
  • a suitable solvent for SbCl 3 is for instance acetone.
  • the salt BiF 3 can be dissolved in HF.
  • a gel-like X-halogen means a X-halogen present as liquid phase or a X-halogen solution each comprising an additional gelling agent and a viscosity in the range of 1 mPa ⁇ s to 250 mPa ⁇ s, preferably 2 mPa ⁇ s to 50 mPa ⁇ s.
  • a gelling agent may be for instance poly-ethylene-glycol (PEG) or other gelling agents known by an expert.
  • a X-halogen suspension means a X-halogen solution, a X-halogen present as liquid phase or a gel-like X-halogen each with dispersed solid particles.
  • Such solid particles provide further doping elements and are suitable for forming Cd-and/or Se-rich layers close to the CdTe based absorber layer, in other words the solid particles may comprise at least Cd and/or Se and doping elements, like for instance a group 15 element, preferably P, As, Sb or Bi, or a group 5 element, for instance V.
  • the solid particles may be for instance doping agents, like Cd 2 As 3 or As 2 Se 3 .
  • the disperse solid particles have a particle size in the range of 1 ⁇ m to 100 ⁇ m.
  • the X-halogen suspension comprises 10 mg to 10 g of solid particles.
  • the X-halogen solution, the X-halogen suspension or the gel-like X-halogen comprises the X-halogen with a concentration in the range of larger than zero (0) (0.1 mmol/L) to 50 mg/L (50 mmol/L) .
  • concentration of SbCl 3 may lie in the range of 5 mg/L to 30 mg/L, especially in the range of 15 mg/L to 25 mg/L.
  • the X-halogen is applied for a time duration in the range of 2 minutes to 10 minutes in step c) .
  • the X-halogen is applied by known methods, like wet chemical impregnation, gaseous impregnation, dip coating, roller coating, etc.
  • step e) the second back contact layer comprising a metal layer is deposited onto a surface of the first back contact layer, if step c) is performed before step d) . If step c) is performed after step d) , the second back contact layer is deposited in step e) onto a dried layer of X-halogen formed on the first back contact layer in the result of the application of the X-halogen in step c) or onto the first back contact layer after the X-halogen is diffused into the grain structure of the first back contact layer in or after step c) .
  • the first back contact layer may be a ZnTe layer or may be a ZnTe based layer.
  • AZnTe based layer may be CdZn x Te 1-x with x varying between 0 ⁇ x ⁇ 0.6 or a doped ZnTe layer, wherein doping elements known from the state of the art may be applied, however excluding copper.
  • the first back contact layer may have a thickness in the range of 5 nm to 100 nm, in particular 10 nm to 50 nm, and further in particular 20 nm to 30 nm.
  • the second back contact layer may be a layer stack comprising at least one metal layer.
  • a metal layer is a highly conductive metal layer with a sheet resistance of ⁇ 1 Ohm/sq, for instance Mo or Al but not limiting.
  • Another layer of the layer stack of the second back contact layer may be a metal nitride layer, for instance MoN, TiN or AlN but not limiting.
  • the metal nitride layer comprises the same metal as the metal layer.
  • the second back contact layer is deposited with a thickness in the range of 20 nm to 150 nm.
  • the second back contact layer may comprise a MoN layer with a thickness in the range of 5 nm to 20 nm and a Mo layer with a thickness of, for instance, 100 nm.
  • the first and the second back contact layer may be deposited by any known method.
  • the first back contact layer and/or the second back contact layer are deposited by sputtering, wherein each sputter deposition is performed at a temperature in the range of room temperature to 300°C. Although these temperatures are relatively low, they are sufficient for diffusion of the X-halogen into the first back contact layer directly during the deposition of the first back contact layer, if the X-halogen is applied before depositing the first back contact layer, and/or during the deposition of the second back contact layer.
  • room temperature means a temperature in the range from 18°C to 40°C.
  • the first and/or the second back contact may be deposited in an inert atmosphere or vacuum.
  • the thermal treatment in step f) is performed after steps c) and d) at a temperature in the range of 230°C to 270°C.
  • This step results in dissociation of the X-halogen and in integration of the element X into the first back contact layer material.
  • the first back contact layer is afterwards a p + layer reducing the Schottky barrier at the interface of the CdTe based absorber layer and the back contact.
  • the thermal treatment in step f) is performed in inert atmosphere or vacuum for a duration in the range of 10 minutes to 60 minutes.
  • an inert atmosphere means an atmosphere with an oxygen content below 50 ppm and free from humidity or a reducing atmosphere like Ar, N 2 or H 2 atmosphere.
  • Vacuum means a pressure in the range of 10 -4 Pa to 10 4 Pa.
  • the method may comprise further steps known from state of the art to manufacture a CdTe based thin film solar cell device, like for instance an NP etching step (phosphorus nitride etch) for forming a Te-rich surface portion on a CdTe based absorber layer or an HCl etching step (hydrogen chloride etch) for cleaning the surface of the CdTe based absorber layer.
  • NP etching step phosphorus nitride etch
  • HCl etching step hydrogen chloride etch
  • a CdTe based thin film solar cell device comprises:
  • the back contact layer stack comprising a first back contact layer comprising ZnTe and a second back contact layer comprising a metal layer, wherein the first back contact layer is formed onthe CdTe based absorber layer and the second back contact layer is formed on the first back contact layer.
  • the first back contact layer is doped with an element selected out of a group consisting of P, As, Sb and V and the element is present in the first back contact layer with a concentration in the range of 10 17 cm -3 to 10 22 cm -3 .
  • the element is present in the first back contact layer with a concentration in the range of 10 18 cm -3 to 10 21 cm -3 , and in particular with a concentration in the range of 10 19 cm -3 to 10 20 cm -3 .
  • At least the first back contact layer is free of copper.
  • the whole CdTe based thin film solar cell device is free of copper. “Free of copper” means that the concentration of copper is less than 10 14 cm -3 .
  • the element the first back contact layer is doped with is present in the CdTe based absorber layer with a concentration lower than 5 ⁇ 10 14 cm -3 . That is, the CdTe based absorber layer is almost not doped with the element the first back contact layer is doped with.
  • the CdTe based thin film solar cell device according to the second aspect of the invention is manufactured with a method according to the first aspect of the invention.
  • Fig. 1 shows a first exemplary process flow of a method according to the invention
  • Fig. 2 shows a second exemplary process flow of a method according to the invention
  • Fig. 3 shows a first exemplary CdTe based thin film solar cell device according to the invention.
  • a process flow of a first exemplary embodiment of a method for manufacturing a CdTe based thin film solar cell device having a copper-free doped back contact according to the invention is shown in Fig. 1.
  • a semi-finished solar cell device comprising at least a substrate, a front electrode and a CdTe based absorber layer is provided (step a) ) .
  • the substrate is a glass substrate and the front electrode is made of tin oxide on top.
  • the CdTe based absorber layer is formed as a single layer of CdTe with a thickness of 3.5 ⁇ m.
  • the CdTe based absorber layer may be formed as a layer stack of different layers of CdSe and CdTe with a total thickness of the layer stack of 3.5 ⁇ m, which may at least partially be intermixed already. However, intermixing may also take place only in the next step of activation treatment.
  • the CdTe based absorber layer may be formed as a doped CdTe based absorber layer, doped with elements known from the state of the art, but advantageously excluding copper.
  • the CdTe based absorber layer may be formed by closed space sublimation, wherein doping may be achieved by methods known from state of the art, for instance by co-deposition of a CdTe based absorber layer and at least one doping material or any other known method.
  • the semi-finished solar cell device may comprise further layers like buffer layers, window layers or any else.
  • an activation treatment is performed (step b) ) by applying an activation agent onto the CdTe based absorber layer by a wet chemical method followed by annealing in air atmosphere at a temperature in the range of 380°C to 470°C for a duration in the range of 7 minutes to 35 minutes and a cleaning step.
  • a X-halogen is applied to a surface of the CdTe based absorber layer (step c) ) , wherein X is selected out of the group consisting of P, As, Sb and V.
  • SbCl 3 is applied as the X-halogen in liquid form as a solution by a wet chemical method known from state of the art. The solution is formed by dissolving 20 mg/L of SbCl 3 in acetone, and the surface of the CdTe based absorber layer is wet-chemical impregnated with the solution for about 5 minutes at room temperature.
  • a first back contact layer is deposited (step d) ) , wherein the first back contact layer comprises ZnTe.
  • the first back contact layer is deposited as a 25 nm thick ZnTe layer by sputter deposition in vacuum at a temperature of about 200°C.
  • a second back contact layer comprising a metal layer is deposited in step S14 (step e) ) .
  • the second back contact layer may be deposited as a layer stack comprising an intermediate metal nitride layer and the metal layer.
  • the metal nitride layer may be formed as a 20 nm thick MoN layer by sputtering Mo at room temperature in the presence of nitrogen.
  • the metal layer is a 100 nm thick Mo layer deposited by sputtering at room temperature.
  • step S15 a thermal treatment is performed (step f) ) at a temperature of 270°C in air for 30 minutes.
  • This treatment causes a dissociation of the SbCl3, a diffusion of the antimony into the first back contact layer, where it is integrated into the ZnTe material.
  • Fig. 2 shows a process flow of a second exemplary embodiment of a method for manufacturing a CdTe based thin film solar cell device having a copper-free doped back contact according to the invention.
  • the second embodiment differs from the first embodiment in that the sequence of the steps c) and d) is changed. That is, steps S20 to S25 are in principle similar or even identical to steps S10 to S15 of the first embodiment shown in Fig. 1, but step d) , i.e. step S22 being similar to step S13, is performed before step c) , i.e. step S23 being similar to step S14. Since the steps of the second embodiment are similar to the steps of the first embodiment, the steps will not be explained in detail again.
  • a semi-finished solar cell device comprising at least a substrate, a front electrode and a CdTe based absorber layer is provided (step a) ) in step S20. Then, an activation treatment is performed (step b) ) in step S21. Afterwards, a first back contact layer comprising ZnTe is deposited on a surface of the CdTe based absorber layer (step d) ) in step S22. In the next step S23, a X-halogen is applied to a surface of the first back contact layer (step c) ) , wherein X is selected out of the group consisting of P, As, Sb and V.
  • SbCl 3 is applied as the X-halogen in liquid form as a solution by a wet chemical method known from state of the art.
  • the solution is formed by dissolving 20 mg/L of SbCl 3 in acetone, and the surface of the first back contact layer is wet-chemical impregnated with the solution for about 5 minutes at room temperature.
  • a second back contact layer comprising a metal layer is deposited in step S24 (step e) ) .
  • a thermal treatment is performed (step f) ) at a temperature of 270°C in air for 30 minutes.
  • Fig. 3 shows a first exemplary CdTe based thin film solar cell device 10 according to the invention, which was manufactured using the method according to the invention, for instance the first exemplary embodiment of the invention.
  • the CdTe based thin film solar cell device 10 comprises a substrate 11, a front electrode 12, a CdTe based absorber layer 13 and a back electrode 14.
  • the substrate 11 is a transparent substrate, for instance glass, which is transparent at least for light with a wavelength which is absorbed by the CdTe based absorber layer 13, i.e. for light with a wavelength between 300 nm and 1200 nm.
  • the front electrode 12 is a transparent front electrode formed for instance of a transparent conductive oxide like tin oxide.
  • the CdTe based absorber layer 13 may be a CdTe layer or a Cd 1-x Hg x Te, Cd 1-x Mn x Te, Cd 1- x Mg x Te or CdSe x Te 1-x layer with x varying between 0 ⁇ x ⁇ 0.5. Nevertheless, the CdTe based absorber layer 13 may also be a layer stack comprising one of the above-mentioned layers and at least one further layer, for instance one or more CdSe layers. Furthermore, the CdTe based absorber layer 13 may be formed as a doped CdTe based absorber layer, doped with any suitable element known from state of the art, wherein advantageously copper is excluded.
  • the CdTe based absorber layer 13 has a thickness in the range of 1 ⁇ m to 5 ⁇ m, preferably with a thickness from 2 ⁇ m to 4 ⁇ m.
  • the back electrode 14 comprises a first back contact layer 141 and a second back contact layer 142.
  • the first back contact layer 141 comprises ZnTe and may be a ZnTe layer or a ZnTe based layer.
  • AZnTe based layer may be CdZn x Te 1-x with x varying between 0 ⁇ x ⁇ 0.6.
  • the first back contact layer has a thickness in the range of 5 nm to 100 nm, in particular 10 nm to 50 nm, and further in particular 20 nm to 30 nm.
  • the first back contact layer 141 is doped with an element selected out of a group consisting of P, As, Sb and V and the element is present in the first back contact layer 141 with a concentration in the range of 10 17 cm -3 to 10 22 cm -3 .
  • the first back contact layer 141 is doped with antimony with a concentration of 1 ⁇ 10 20 cm -3 .
  • the second back contact layer 142 comprises a metal layer and may be a layer stack further comprising further layers.
  • the second back contact layer 142 is a layer stack comprising a 20 nm thick MoN layer on the first back contact layer 141 and a 100 nm thick Mo layer on the MoN layer.
  • the CdTe based thin film solar cell device 10 is free of copper, i.e. the CdTe based absorber layer 13 and the back electrode 14 are free of copper. “Free of copper” means that the concentration of copper in each of these layers is less than 10 14 cm -3 .
  • the exemplary CdTe based thin film solar cell device 10 manufactured by the first exemplary embodiment of the method shown in Fig. 1 exhibits an efficiency up to 16.6%and an antimony concentration of about 10 14 cm -3 in the CdTe based absorber layer 13. That is, the CdTe based absorber layer is almost not doped with Sb.
  • An exemplary CdTe based thin film solar cell device manufactured by the second exemplary embodiment of the method shown in Fig. 2 exhibits an efficiency up to 15.1%and an antimony concentration of about 2.5 ⁇ 10 14 cm -3 in the CdTe based absorber layer. That is, the CdTe based absorber layer is again almost not doped with Sb.

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Abstract

A method for manufacturing a CdTe based thin film solar cell device comprising a copper-free doped back contact and a CdTe based thin film solar cell device. The method comprises at least the following steps: a) providing a semifinished solar cell device comprising at least a substrate, a front electrode and a CdTe based absorber layer (S10), b) performing an activation treatment of the CdTe based absorber layer (S11), c) applying a X-halogen, wherein X is selected out of a group consisting of P, As, Sb, Bi and V (S12), d) depositing a first back contact layer comprising ZnTe (S13), e) depositing a second back contact layer comprising a metal layer (S14), and f) performing a thermal treatment (S15). In the method, step c) is performed after step b) and directly before or after step d), wherein no thermal treatment step is performed between step c) and d) if step c) is performed before step d). Further, the thermal treatment in step f) is performed after steps c) and d) at temperatures in the range of 230℃ to 270℃.

Description

Method for manufacturing a CdTe based thin film solar cell device comprising a doped back contact and such a CdTe based thin film solar cell device
The invention concerns a CdTe based thin film solar cell device comprising a doped back contact, wherein the back contact is copper-free, and a method for forming such a CdTe based thin film solar cell device.
A CdTe based thin film solar cell device is a solar cell device comprising a CdTe based thin film as a photoactive layer also called an absorber layer. For a back contact, different materials are known. For instance, Hall et. al. describes in “Back contacts materials used in thin film CdTe solar cells–A review” , Energy Sci Eng. 2021 (9) that a layer stack comprising a ZnTe layer at the interface to the CdTe based absorber layer and a metal layer on the ZnTe layer is a proper back contact. The ZnTe layer may be doped, for instance with copper. Copper as doping element has some advantages, like reducing the Shottky barrier between the absorber layer and the back contact. However, copper has also some drawbacks, like low device stability and charge carrier lifetime, because it diffuses easily into and within the CdTe based absorber layer. Therefore, antimon was used as doping element, wherein the doped ZnTe layer, i.e. ZnTe: Sb, was spin-coated onto the CdTe absorber layer.
However, forming the ZnTe layer as a doped layer during deposition, i.e. during spin-coating or sputtering, causes problems with respect to the control of the amount of the doping element and with respect to the process conditions during deposition of the ZnTe layer.
Object of the invention is to provide an alternative method for manufacturing a CdTe based thin film solar cell device comprising a copper-free doped back contact and, in the result, a CdTe based thin film solar cell device with improved photovoltaic efficiency and long-term stability.
The object is solved by a method and a device according to the independent claims. Preferred embodiments are subject of the dependent claims.
According to a first aspect of the invention, a method for manufacturing a CdTe based thin film solar cell device having a copper-free doped back contact at least comprises the following steps:
a) Providing a semi-finished solar cell device comprising at least a substrate, a front electrode and a CdTe based absorber layer,
b) Performing an activation treatment of the CdTe based absorber layer,
c) Applying a X-halogen, wherein X is selected out of a group consisting of P, As, Sb, Bi and V,
d) Depositing a first back contact layer comprising ZnTe,
e) Depositing a second back contact layer comprising a metal layer,
f) Performing a thermal treatment,
wherein step c) is performed after step b) and directly before or after step d) , wherein no thermal treatment step is performed between step c) and d) if step c) is performed before step d) , and wherein the thermal treatment in step f) is performed after steps c) and d) at a temperature in the range of 230℃ to 270℃.
Advantageously, this method enables manufacturing a CdTe based thin film solar cell device having a copper-free doped back contact by ex-situ doping.
According to the invention, asubstrate means any basis the front electrode and the CdTe based absorber layer is formed onto in the semi-finished solar cell device provided in step a) . That is, the substrate may comprise a transparent base substrate, for instance of glass or polymeric material. The front electrode may be a transparent front electrode, for instance made of a transparent conductive oxide. In embodiments, the semi-finished solar cell device may comprise further layers like buffer layers, window layers, antireflective layers or any else, wherein the further layers may be formed between the substrate and the front electrode or between the front electrode and the CdTe based absorber layer.
A CdTe based absorber layer means a layer or layer stack comprising at least one layer of the composition CdTe, Cd1-xHgxTe, Cd1-xMnxTe, Cd1-xMgxTe or CdSexTe1-x with x varying between 0≤x≤0.5. The layer stack may comprise further layers, for instance one or more CdSe layers. In embodiments, the individual layers of such a layer stack may be formed, for instance, by subsequently depositing one or a plurality of layers, for instance layers of CdSe and CdTe, followed by interdiffusion of the different layers if desired, or in one undivided process. In embodiments, the CdTe based absorber layer is formed as a doped CdTe based absorber layer, doped with any suitable element known from state of the art, wherein advantageously copper is excluded. Such a doped CdTe based absorber layer may be achieved by any known method, for instance by comprising one or more doping source layers into the CdTe based absorber layer stack or by depositing a doped CdTe based absorber layer using co-deposition of a CdTe based material and at least one doping material. In embodiments, the CdTe based absorber layer is doped with a group 15 element, preferably with P, As, Sb or Bi, or a group 5 element, for instance V. In further embodiments, the CdTe based absorber layer may be formed using any technique known from the prior art, comprising, but not limited to, physical vapour deposition, e.g. sputtering, evaporation or sublimation, electrodeposition, or any else. In  embodiments, the CdTe based absorber layer is deposited with a thickness from 1μm to 5μm, preferably with a thickness from 2μm to 4μm.
The activation treatment in step b) results in a CdTe based absorber layer with passivated grain boundaries and saturated defects. In embodiments, the activation treatment in step b) comprises applying an activation agent which is a chlorine comprising material, like for instance CdCl2, to a surface of the CdTe based absorber layer and performing a thermal treatment at a temperature in the range of 380℃ to 480℃. The activation agent may be applied by wet chemical methods or by vacuum evaporation. The thermal treatment, also called annealing, may be performed in air atmosphere for a duration in the range of 5 minutes to 30 minutes. After the thermal treatment, acleaning step may be performed in order to remove residues of the activation agent from the surface of the CdTe based absorber layer. Step b) is always performed after step a) and before step c) .
In step c) , the X-halogen is applied, wherein this step may be performed directly before or after depositing the first back contact layer comprising ZnTe, i.e. directly before or after step d) . If step c) is performed before step d) , the X-halogen is applied to the surface of the activated CdTe based absorber layer. Due to the activation treatment performed before, the element X or the X-halogen does not diffuse into the CdTe based absorber layer, but diffuses instead into the first back contact layer comprising ZnTe which is deposited afterwards. If step c) is performed after step d) , the X-halogen is applied to a surface of the first back contact layer. In embodiments where step c) is performed before step d) , the X-halogen is applied in liquid form in step c) , in other embodiments the X-halogen may be applied also in gaseous form in step c) . Examples for X-halogens, wherein X is selected out of a group consisting of P, As, Sb, Bi and V are but not limiting PCl3, AsCl3, SbCl3, BiCl3, VF5, VCl4, VCl3. AX-halogen in liquid form means a X-halogen present as liquid phase, a X-halogen solution, a X-halogen suspension or a gel-like X-halogen.
A X-halogen present as liquid phase is for instance PCl3, AsCl3, VF5, VCl4, which are present as liquid phase at room temperature.
A X-halogen solution means an X-halogen dissolved in a solvent. The solvent is thereby suitable for solving the X-halogen. Asuitable solvent for VF5 is for instance water, asuitable solvent for AsCl3 and PCl3 is for instance ether, and a suitable solvent for SbCl3 is for instance acetone. The salt BiF3 can be dissolved in HF.
A gel-like X-halogen means a X-halogen present as liquid phase or a X-halogen solution each comprising an additional gelling agent and a viscosity in the range of 1 mPa·s to 250 mPa·s,  preferably 2 mPa·s to 50 mPa·s. Such a gelling agent may be for instance poly-ethylene-glycol (PEG) or other gelling agents known by an expert.
A X-halogen suspension means a X-halogen solution, a X-halogen present as liquid phase or a gel-like X-halogen each with dispersed solid particles. Such solid particles provide further doping elements and are suitable for forming Cd-and/or Se-rich layers close to the CdTe based absorber layer, in other words the solid particles may comprise at least Cd and/or Se and doping elements, like for instance a group 15 element, preferably P, As, Sb or Bi, or a group 5 element, for instance V. In embodiments, the solid particles may be for instance doping agents, like Cd2As3 or As2Se3. In embodiments, the disperse solid particles have a particle size in the range of 1μm to 100μm. In further embodiment, the X-halogen suspension comprises 10 mg to 10 g of solid particles.
In further embodiments, the X-halogen solution, the X-halogen suspension or the gel-like X-halogen comprises the X-halogen with a concentration in the range of larger than zero (0) (0.1 mmol/L) to 50 mg/L (50 mmol/L) . In particular in the case of SbCl3 present in a solution, the concentration of SbCl3 may lie in the range of 5 mg/L to 30 mg/L, especially in the range of 15 mg/L to 25 mg/L.
In some embodiments where step c) is performed after step d) , alternatively or additionally, a X-hydride is applied to the CdTe based absorber layer in step c) , wherein X is selected out of a group consisting of P, As, Sb, Bi and V. Examples for X-hydrides but not limiting are PH3, AsH3, SbH3, BiH3, VH5. Advantageously, X-hydrides are present as gaseous phase at room temperature, i.e. in a temperature range between 18℃ to 40℃.
In embodiments, the X-halogen is applied for a time duration in the range of 2 minutes to 10 minutes in step c) . In embodiments, the X-halogen is applied by known methods, like wet chemical impregnation, gaseous impregnation, dip coating, roller coating, etc.
In step d) , the first back contact layer comprising ZnTe is deposited onto the surface of the activated CdTe absorber layer, if step c) is performed after step d) , or onto a dried layer of X-halogen formed on the activated CdTe absorber layer in the result of the application of the X-halogen in step c) , if step c) is performed before step d) .
In step e) , the second back contact layer comprising a metal layer is deposited onto a surface of the first back contact layer, if step c) is performed before step d) . If step c) is performed after step d) , the second back contact layer is deposited in step e) onto a dried layer of X-halogen formed on the first back contact layer in the result of the application of the X-halogen in step c)  or onto the first back contact layer after the X-halogen is diffused into the grain structure of the first back contact layer in or after step c) .
The first back contact layer may be a ZnTe layer or may be a ZnTe based layer. AZnTe based layer may be CdZnxTe1-x with x varying between 0≤x≤0.6 or a doped ZnTe layer, wherein doping elements known from the state of the art may be applied, however excluding copper. The first back contact layer may have a thickness in the range of 5 nm to 100 nm, in particular 10 nm to 50 nm, and further in particular 20 nm to 30 nm.
The second back contact layer may be a layer stack comprising at least one metal layer. In embodiments, such a metal layer is a highly conductive metal layer with a sheet resistance of <1 Ohm/sq, for instance Mo or Al but not limiting. Another layer of the layer stack of the second back contact layer may be a metal nitride layer, for instance MoN, TiN or AlN but not limiting. In embodiments, the metal nitride layer comprises the same metal as the metal layer. In embodiments, the second back contact layer is deposited with a thickness in the range of 20 nm to 150 nm. For example, the second back contact layer may comprise a MoN layer with a thickness in the range of 5 nm to 20 nm and a Mo layer with a thickness of, for instance, 100 nm.
The first and the second back contact layer may be deposited by any known method. In embodiments, the first back contact layer and/or the second back contact layer are deposited by sputtering, wherein each sputter deposition is performed at a temperature in the range of room temperature to 300℃. Although these temperatures are relatively low, they are sufficient for diffusion of the X-halogen into the first back contact layer directly during the deposition of the first back contact layer, if the X-halogen is applied before depositing the first back contact layer, and/or during the deposition of the second back contact layer. According to the invention, room temperature means a temperature in the range from 18℃ to 40℃. The first and/or the second back contact may be deposited in an inert atmosphere or vacuum.
According to the invention, the thermal treatment in step f) is performed after steps c) and d) at a temperature in the range of 230℃ to 270℃. This step results in dissociation of the X-halogen and in integration of the element X into the first back contact layer material. Advantageously, the first back contact layer is afterwards a p+layer reducing the Schottky barrier at the interface of the CdTe based absorber layer and the back contact.
“After steps c) and d) ” means that at least these both steps have to be performed in any order before performing step f) . In embodiments, the thermal treatment in step f) is performed after step e) . Therefore, there are the following possible embodiments of the sequence of steps according to the invention:
● a) –b) –c) –d) –e) –f)
● a) –b) –d) –c) –e) –f)
● a) –b) –c) –d) –f) –e)
● a) –b) –d) –c) –f) –e)
In embodiments, the thermal treatment in step f) is performed in inert atmosphere or vacuum for a duration in the range of 10 minutes to 60 minutes.
According to the invention, an inert atmosphere means an atmosphere with an oxygen content below 50 ppm and free from humidity or a reducing atmosphere like Ar, N2 or H2 atmosphere. Vacuum means a pressure in the range of 10-4 Pa to 104 Pa.
In further embodiments, the method may comprise further steps known from state of the art to manufacture a CdTe based thin film solar cell device, like for instance an NP etching step (phosphorus nitride etch) for forming a Te-rich surface portion on a CdTe based absorber layer or an HCl etching step (hydrogen chloride etch) for cleaning the surface of the CdTe based absorber layer.
According to a second aspect of the invention, a CdTe based thin film solar cell device comprises:
- a substrate
- a front electrode formed on the substrate,
- a CdTe based absorber layer formed on the front electrode, and
- a back contact layer stack formed on the CdTe based absorber layer, the back contact layer stack comprising a first back contact layer comprising ZnTe and a second back contact layer comprising a metal layer, wherein the first back contact layer is formed onthe CdTe based absorber layer and the second back contact layer is formed on the first back contact layer.
According to the invention, the first back contact layer is doped with an element selected out of a group consisting of P, As, Sb and V and the element is present in the first back contact layer with a concentration in the range of 1017 cm-3 to 1022 cm-3. In embodiments, the element is present in the first back contact layer with a concentration in the range of 1018 cm-3 to 1021 cm-3, and in particular with a concentration in the range of 1019 cm-3 to 1020 cm-3.
In embodiments, at least the first back contact layer is free of copper. In further embodiments, the whole CdTe based thin film solar cell device is free of copper. “Free of copper” means that the concentration of copper is less than 1014 cm-3.
In embodiments, the element the first back contact layer is doped with is present in the CdTe based absorber layer with a concentration lower than 5·1014 cm-3. That is, the CdTe based absorber layer is almost not doped with the element the first back contact layer is doped with.
Advantageously, the CdTe based thin film solar cell device according to the second aspect of the invention is manufactured with a method according to the first aspect of the invention.
For realization of the invention, it is advantageous to combine the described embodiments and features of the claims as described above. However, the embodiments of the invention described in the foregoing description are examples given by way of illustration and the invention is nowise limited thereto. Any modification, variation and equivalent arrangement as well as combinations of embodiments should be considered as being included within the scope of the invention.
Exemplary embodiments
The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles. Other embodiments of the invention and many of the intended advantages will be readily appreciated, as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numbers designate corresponding similar parts.
Fig. 1 shows a first exemplary process flow of a method according to the invention,
Fig. 2 shows a second exemplary process flow of a method according to the invention, and
Fig. 3 shows a first exemplary CdTe based thin film solar cell device according to the invention.
A process flow of a first exemplary embodiment of a method for manufacturing a CdTe based thin film solar cell device having a copper-free doped back contact according to the invention is shown in Fig. 1. First in step S10, a semi-finished solar cell device comprising at least a substrate, a front electrode and a CdTe based absorber layer is provided (step a) ) . The substrate is a glass substrate and the front electrode is made of tin oxide on top. The CdTe based absorber layer is formed as a single layer of CdTe with a thickness of 3.5μm. In other embodiments, the CdTe based absorber layer may be formed as a layer stack of different layers  of CdSe and CdTe with a total thickness of the layer stack of 3.5μm, which may at least partially be intermixed already. However, intermixing may also take place only in the next step of activation treatment. In other embodiments, the CdTe based absorber layer may be formed as a doped CdTe based absorber layer, doped with elements known from the state of the art, but advantageously excluding copper. The CdTe based absorber layer may be formed by closed space sublimation, wherein doping may be achieved by methods known from state of the art, for instance by co-deposition of a CdTe based absorber layer and at least one doping material or any other known method. In other embodiments, the semi-finished solar cell device may comprise further layers like buffer layers, window layers or any else.
In the following step S11, an activation treatment is performed (step b) ) by applying an activation agent onto the CdTe based absorber layer by a wet chemical method followed by annealing in air atmosphere at a temperature in the range of 380℃ to 470℃ for a duration in the range of 7 minutes to 35 minutes and a cleaning step. In the next step S12, a X-halogen is applied to a surface of the CdTe based absorber layer (step c) ) , wherein X is selected out of the group consisting of P, As, Sb and V. In the example, SbCl3 is applied as the X-halogen in liquid form as a solution by a wet chemical method known from state of the art. The solution is formed by dissolving 20 mg/L of SbCl3 in acetone, and the surface of the CdTe based absorber layer is wet-chemical impregnated with the solution for about 5 minutes at room temperature.
Following in step S13, a first back contact layer is deposited (step d) ) , wherein the first back contact layer comprises ZnTe. For instance, the first back contact layer is deposited as a 25 nm thick ZnTe layer by sputter deposition in vacuum at a temperature of about 200℃. Then, a second back contact layer comprising a metal layer is deposited in step S14 (step e) ) . The second back contact layer may be deposited as a layer stack comprising an intermediate metal nitride layer and the metal layer. For instance, the metal nitride layer may be formed as a 20 nm thick MoN layer by sputtering Mo at room temperature in the presence of nitrogen. In the present example, the metal layer is a 100 nm thick Mo layer deposited by sputtering at room temperature.
Afterwards in step S15, a thermal treatment is performed (step f) ) at a temperature of 270℃ in air for 30 minutes. This treatment causes a dissociation of the SbCl3, a diffusion of the antimony into the first back contact layer, where it is integrated into the ZnTe material.
Fig. 2 shows a process flow of a second exemplary embodiment of a method for manufacturing a CdTe based thin film solar cell device having a copper-free doped back contact according to the invention. The second embodiment differs from the first embodiment in that the sequence of the steps c) and d) is changed. That is, steps S20 to S25 are in principle similar or even  identical to steps S10 to S15 of the first embodiment shown in Fig. 1, but step d) , i.e. step S22 being similar to step S13, is performed before step c) , i.e. step S23 being similar to step S14. Since the steps of the second embodiment are similar to the steps of the first embodiment, the steps will not be explained in detail again.
According to the second embodiment, a semi-finished solar cell device comprising at least a substrate, a front electrode and a CdTe based absorber layer is provided (step a) ) in step S20. Then, an activation treatment is performed (step b) ) in step S21. Afterwards, a first back contact layer comprising ZnTe is deposited on a surface of the CdTe based absorber layer (step d) ) in step S22. In the next step S23, a X-halogen is applied to a surface of the first back contact layer (step c) ) , wherein X is selected out of the group consisting of P, As, Sb and V. In the example, SbCl3 is applied as the X-halogen in liquid form as a solution by a wet chemical method known from state of the art. The solution is formed by dissolving 20 mg/L of SbCl3 in acetone, and the surface of the first back contact layer is wet-chemical impregnated with the solution for about 5 minutes at room temperature. Then, a second back contact layer comprising a metal layer is deposited in step S24 (step e) ) . Afterwards in step S25, a thermal treatment is performed (step f) ) at a temperature of 270℃ in air for 30 minutes.
Fig. 3 shows a first exemplary CdTe based thin film solar cell device 10 according to the invention, which was manufactured using the method according to the invention, for instance the first exemplary embodiment of the invention. The CdTe based thin film solar cell device 10 comprises a substrate 11, a front electrode 12, a CdTe based absorber layer 13 and a back electrode 14. The substrate 11 is a transparent substrate, for instance glass, which is transparent at least for light with a wavelength which is absorbed by the CdTe based absorber layer 13, i.e. for light with a wavelength between 300 nm and 1200 nm. The front electrode 12 is a transparent front electrode formed for instance of a transparent conductive oxide like tin oxide. The CdTe based absorber layer 13 may be a CdTe layer or a Cd1-xHgxTe, Cd1-xMnxTe, Cd1- xMgxTe or CdSexTe1-x layer with x varying between 0≤x≤0.5. Nevertheless, the CdTe based absorber layer 13 may also be a layer stack comprising one of the above-mentioned layers and at least one further layer, for instance one or more CdSe layers. Furthermore, the CdTe based absorber layer 13 may be formed as a doped CdTe based absorber layer, doped with any suitable element known from state of the art, wherein advantageously copper is excluded. The CdTe based absorber layer 13 has a thickness in the range of 1μm to 5μm, preferably with a thickness from 2μm to 4μm.
The back electrode 14 comprises a first back contact layer 141 and a second back contact layer 142. The first back contact layer 141 comprises ZnTe and may be a ZnTe layer or a ZnTe  based layer. AZnTe based layer may be CdZnxTe1-x with x varying between 0≤x≤0.6. The first back contact layer has a thickness in the range of 5 nm to 100 nm, in particular 10 nm to 50 nm, and further in particular 20 nm to 30 nm. According to the invention, the first back contact layer 141 is doped with an element selected out of a group consisting of P, As, Sb and V and the element is present in the first back contact layer 141 with a concentration in the range of 1017 cm-3 to 1022 cm-3. In the present example, the first back contact layer 141 is doped with antimony with a concentration of 1·1020 cm-3.
The second back contact layer 142 comprises a metal layer and may be a layer stack further comprising further layers. For instance, the second back contact layer 142 is a layer stack comprising a 20 nm thick MoN layer on the first back contact layer 141 and a 100 nm thick Mo layer on the MoN layer.
The CdTe based thin film solar cell device 10 is free of copper, i.e. the CdTe based absorber layer 13 and the back electrode 14 are free of copper. “Free of copper” means that the concentration of copper in each of these layers is less than 1014 cm-3.
The exemplary CdTe based thin film solar cell device 10 manufactured by the first exemplary embodiment of the method shown in Fig. 1 exhibits an efficiency up to 16.6%and an antimony concentration of about 1014 cm-3 in the CdTe based absorber layer 13. That is, the CdTe based absorber layer is almost not doped with Sb.
An exemplary CdTe based thin film solar cell device manufactured by the second exemplary embodiment of the method shown in Fig. 2 exhibits an efficiency up to 15.1%and an antimony concentration of about 2.5●1014 cm-3 in the CdTe based absorber layer. That is, the CdTe based absorber layer is again almost not doped with Sb.
The embodiments of the invention described in the foregoing description are examples given by way of illustration and the invention is nowise limited thereto. Any modification, variation and equivalent arrangement as well as combinations of embodiments should be considered as being included within the scope of the invention.
Reference signs
10         CdTe based thin film solar cell device
11         Substrate
12         Front electrode
13         CdTe based absorber layer
14         Back electrode
141        First back contact layer
142        Second back contact layer

Claims (12)

  1. Method for manufacturing a CdTe based thin film solar cell device comprising a copper-free doped back contact, the method at least comprising the following steps:
    a) Providing a semifinished solar cell device comprising at least a substrate, a front electrode and a CdTe based absorber layer,
    b) Performing an activation treatment of the CdTe based absorber layer,
    c) Applying a X-halogen, wherein X is selected out of a group consisting of P, As, Sb, Bi and V,
    d) Depositing a first back contact layer comprising ZnTe,
    e) Depositing a second back contact layer comprising a metal layer,
    f) Performing a thermal treatment,
    wherein
    - step c) is performed after step b) and directly before or after step d) , wherein no thermal treatment step is performed between step c) and d) if step c) is performed before step d) , and
    - the thermal treatment in step f) is performed after steps c) and d) at a temperature in the range of 230℃ to 270℃.
  2. Method according to claim 1, characterized in that the thermal treatment in step f) is performed after step e) .
  3. Method according to claim 1 or 2, characterized in that the thermal treatment in step f) is performed) in inert atmosphere or vacuum for a duration in the range of 10 minutes to 60 minutes.
  4. Method according to any of the previous claims, characterized in that the X-halogen is applied in step c) in liquid form.
  5. Method according to claim 4, characterized in that the X-halogen is applied in liquid form in a solution with a content of the X-halogen in a range of larger than zero to 50 mg/L.
  6. Method according to any of the previous claims, characterized in that the X-halogen is applied for a time duration in the range of 2 minutes to 10 minutes.
  7. Method according to any of the previous claims, characterized in that the activation treatment of the CdTe based absorber layer in step b) comprises applying a chlorine comprising material to a surface of the CdTe based absorber layer and performing a thermal treatment at a temperature in the range of 380℃ to 480℃.
  8. Method according to any of the previous claims, characterized in that the first back contact layer is deposited as a sputtered ZnTe layer.
  9. Method according to any of the previous claims, characterized in that the second back contact layer is deposited as a layer stack by sputtering and comprising at least one metal layer.
  10. Method according to claim 8 or 9, characterized in that each sputter deposition is performed at a temperature in the range of room temperature to 300℃.
  11. CdTe based thin film solar cell device comprising:
    - a substrate
    - a front electrode formed on the substrate,
    - a CdTe based absorber layer formed on the front electrode, and
    - a back contact layer stack formed on the CdTe based absorber layer, the back contact layer stack comprising a first back contact layer comprising ZnTe and a second back contact layer comprising a metal layer, wherein the first back contact layer is formed on the CdTe based absorber layer and the second back contact layer is formed on the first back contact layer,
    characterized in that the first back contact layer is doped with an element selected out of a group consisting of P, As, Sb, Bi and V and the element is present in the first back contact layer with a concentration in the range of 1017 cm-3 to 1022 cm-3.
  12. CdTe based thin film solar cell device according to claim 11, wherein the element the first back contact layer is doped with is present in the CdTe based absorber layer with a concentration lower than 5·1014 cm-3.
PCT/CN2023/117327 2023-09-06 2023-09-06 Method for manufacturing a cdte based thin film solar cell device comprising a doped back contact and such a cdte based thin film solar cell device Pending WO2025050323A1 (en)

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CN102244110A (en) * 2011-06-24 2011-11-16 四川大学 CdTe solar cell by using V-Se film as back contact layer
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CN102244110A (en) * 2011-06-24 2011-11-16 四川大学 CdTe solar cell by using V-Se film as back contact layer
CN102629630A (en) * 2012-04-17 2012-08-08 成都中光电阿波罗太阳能有限公司 Back contact layer and method of manufacturing same on cadmium telluride thin film solar cell
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