A thin-film solar cell and an element doping method for an absorption layer thereof

Abstract

This invention discloses a method for element doping of a thin-film solar cell and its absorber layer, relating to the field of thin-film solar cell technology. By immersing the activated absorber layer in a salt solution of a predetermined dopant element and simultaneously applying an exogenous inducing variable, the predetermined element is doped. During the doping process, the diffusion of dopant ions into the grain boundaries and lattice interior of the absorber layer is promoted, ensuring that the element is not affected by the surface morphology, hydrophilicity / hydrophobicity, internal or edge structure of the absorber layer. This solves the problems of difficult-to-control element doping uniformity, poor process stability, and low effective doping activation rate in existing technologies. It achieves the goal of diffusive doping of p-type elements in the absorber layer with high doping uniformity, high doping activation rate, controllable doping process, and compatibility with existing processes.

Description

Technical Field

[0001] This invention relates to the field of thin-film solar cell technology, and in particular to a method for element doping of a thin-film solar cell and its absorber layer. Background Technology

[0002] Thin-film solar cells are photovoltaic devices made by depositing photoelectric conversion materials on substrates such as glass, plastic, and metal foil. Among them, cadmium telluride (CdTe) thin-film solar cells are one of the most successfully industrialized thin-film photovoltaic technologies. Currently, the world's highest efficiency for CdTe thin-film solar cells is 23.1%, which is still significantly lower than the theoretical maximum conversion efficiency. Factors limiting the improvement of open-circuit voltage and fill factor in CdTe thin-film solar cells are also long-standing bottlenecks restricting performance improvement; for example, low carrier concentration in the absorber layer (10⁻⁶ ppm) is a significant limitation. 14 cm -3 ) and short lifetime (<10 ns).

[0003] Currently, the commonly used doping method for cadmium telluride absorber layers is Cu doping. However, this doping method cannot effectively increase the bulk carrier concentration of the absorber layer, and Cu has a relatively large diffusion coefficient (10⁻⁶). -12 cm 2 / s, 300 K) will affect the long-term stability of the battery; as an alternative to Cu doping, doping CdTe with elements such as group V can achieve effective and stable p-type doping, which can ensure and improve carrier lifetime while increasing carrier concentration, thereby breaking through the existing technical bottleneck and achieving higher conversion efficiency and stability.

[0004] Studies have shown that there are two technical approaches to p-type element doping in polycrystalline CdTe thin films. One is in-situ doping, where element doping is achieved simultaneously during CdTe film deposition in a cadmium-rich pressure environment, followed by high-temperature activation in a reducing atmosphere to activate the dopant element. This method requires highly sophisticated film deposition and activation equipment, and process control is challenging. The other approach is post-diffusion doping, where a group V halide solution is spin-coated onto the CdTe film surface at room temperature in an inert atmosphere after CdTe film deposition and activation, followed by heat treatment to incorporate the element into the absorber layer. This method has lower equipment requirements and has attracted numerous researchers to conduct related studies. However, using this method... In traditional methods, during the doping process, the spin-coating solution and the amount of element doping are easily affected by the morphology, hydrophilicity / hydrophobicity, internal or edge structure of the absorber layer, making it difficult to control the amount and uniformity of element doping, resulting in uneven distribution of doped elements. Furthermore, the separation of the doping element application process from the high-temperature diffusion doping process leads to poor process stability and controllability. Limited by the polycrystalline microstructure, the effective doping activation rate of element diffusion doping driven by single heating is low. Therefore, developing a diffusion doping technology for p-type elements in the absorber layer that features high doping uniformity, high doping activation rate, controllable doping process, and compatibility with existing processes has significant application value and market potential. Summary of the Invention

[0005] The main objective of this invention is to provide a method for elemental doping of a thin-film solar cell and its absorber layer. This method aims to solve the problems in the prior art where the elemental doping amount is affected by the morphology, hydrophilicity / hydrophobicity, internal or edge structure of the absorber layer during diffusion doping, making it difficult to control the elemental doping amount and uniformity. This results in uneven distribution of doped elements, poor process stability, and low effective doping activation rate. The invention achieves the goal of diffusion doping of p-type elements in the absorber layer with high doping uniformity, high doping activation rate, controllable doping process, and compatibility with existing processes.

[0006] To achieve the above objectives, the present invention provides a method for elemental doping of the absorber layer of a thin-film solar cell. The elemental doping method is an exogenously induced immersion liquid-phase doping method, comprising the following steps:

[0007] The activated absorber layer is immersed in a salt solution containing a preset dopant element, heated to a preset temperature, and an exogenous inducing variable is applied. After a preset time, the preset element doping is completed.

[0008] Optionally, the material of the absorber layer includes CdTe and CdSe. x Te 1-x and at least one of CdSe, wherein the CdSe x Te 1-x The value of x in the equation ranges from 0% to 40%.

[0009] Optionally, the exogenous induced variables include, but are not limited to, pressure, electric field, and magnetic field.

[0010] Optionally, the salt solution of the preset dopant element includes at least one of group I element salt solution, group V element salt solution, and group VII element salt solution.

[0011] Optionally, the preset temperature is 50℃~300℃, and the preset duration is ≤100min.

[0012] Optionally, when the exogenous induced variable is pressure, the pressure is 0.01MPa~5MPa; when the exogenous induced variable is electric field, the electric field is 1V / m~100kV / m; when the exogenous induced variable is magnetic field, the magnetic field is 1G~10000G.

[0013] Optionally, the element doping method further includes heat treatment of the absorber layer that has undergone preset element doping, wherein the heat treatment temperature is ≤400℃ and the duration is ≤60min.

[0014] Optionally, the concentration of the Group I element salt solution is 0.01 mmol to 10 mmol, the concentration of the Group V element salt solution is 0.01 mmol to 10 mmol, and the concentration of the Group VII element salt solution is 0.01 mmol to 0.1 mol.

[0015] To achieve the above objectives, the present invention also provides a thin-film solar cell, which includes a substrate, a transparent conductive oxide layer, an absorber layer, a back contact layer, and a back electrode layer. The absorber layer is subjected to element doping after activation treatment, and the element doping method is as described above.

[0016] Optionally, the thin-film solar cell further includes an antireflection film, a sodium-blocking layer, a high-resistivity layer, and a passivation layer. The antireflection film is disposed on one side of the substrate, the sodium-blocking layer is deposited on the substrate, the high-resistivity layer is deposited on the transparent conductive oxide layer, and the passivation layer is deposited on the absorption layer and / or the back contact layer.

[0017] Compared with the prior art, the beneficial effects that the present invention can achieve are as follows:

[0018] 1. Compared with existing methods of element doping using spin-coating surface coating, the present invention employs an immersion-type liquid-phase doping method. This method first immerses the activated absorber layer in a salt solution containing a pre-selected dopant element. Under a specific salt solution concentration, the doping concentration of the pre-selected dopant element is uniform, constant, and controllable, unaffected by the diffusion degree of element ions during subsequent doping. Simultaneously, by applying an exogenous inducing variable, not only can the diffusion of pre-selected dopant element ions into the grain boundaries and lattice of the absorber layer be promoted, but the doping process is also unaffected by the surface morphology, hydrophilicity / phobicity, internal or edge structure of the absorber layer. This results in an absorber layer with uniform dopant element distribution, solving the problems of difficulty in controlling doping uniformity, uneven element distribution, poor process stability, and low effective doping activation rate in existing diffusion doping processes. The invention achieves the goal of diffusion doping of p-type elements in the absorber layer with high doping uniformity, high doping activation rate, controllable doping process, and compatibility with existing processes.

[0019] 2. In the technical solution of the present invention, the immersion liquid phase doping method with simultaneous application of exogenous inducing variables can realize the coordinated introduction of the preset dopant element and the diffusion doping process, so that the dopant element is not affected by the external environment during the doping process, and the doping process can be completed simultaneously in the environment of uniform heating in the liquid phase, without the need to be carried out in an inert gas atmosphere.

[0020] 3. In the technical solution of the present invention, by applying exogenous inducing variables, such as pressure, electric field, and magnetic field, to induce or assist, kinetic assistance is achieved in the immersion liquid phase doping process, which promotes the diffusion and effective doping of the preset doping element, while expanding the process window of thermodynamic doping and reducing the dependence on single high-temperature doping.

[0021] 4. In the technical solution of the present invention, when the salt solution of the preset dopant element is a salt solution of any one of Group I, Group V, and Group VII elements, and is a single-element salt solution, single-element doping can be achieved; when it is a mixed salt solution of any one of Group I elements or multiple elements from multiple groups, multiple-element co-doping can be achieved; the absorption layer element doping method provided by the present invention is applicable to single-element doping, multi-element co-doping, and multi-concentration, multi-element sequential doping; at the same time, exogenous induced variables can help adjust the doping process parameters; the doping method in the technical solution of the present invention is process-independent, which improves its compatibility with other equipment or processes; in addition, the doping method described in the present invention is carried out on an activated absorption layer, which reduces the stringent requirements on equipment and doping conditions during the doping process.

[0022] 5. The absorption layer element doping method provided by this invention has low energy consumption and low cost, and the waste generated during the doping process can be recycled. It is applicable to elements including CdTe and CdSe. x Te 1-x Liquid-phase doping of the absorber layer with at least one of CdSe can improve the electrical properties and device performance of the absorber layer; the process of this elemental doping method is completed at a low temperature of ≤300℃ and is compatible with existing mature production line equipment; secondly, the elemental doping method of this invention can also be applied to thin film stacks activated by conventional process parameters, and it achieves compatibility with subsequent electrode preparation technology.

[0023] 6. In the technical solution of the present invention, element doping can increase the carrier concentration of the absorption layer, thereby improving the photoelectric conversion efficiency and stability of the thin-film solar cell. Attached Figure Description

[0024] Figure 1 This is a schematic flowchart of the element doping method of the present invention;

[0025] Figure 2 The current density-voltage (JV) characteristic curves of the thin-film solar cells of Example 1 and Comparative Example 1 are shown.

[0026] Figure 3 The images show secondary ion mass spectrometry (SIMS) analysis results of the absorption layers doped with Sb and Bi elements obtained in Example 2 and Comparative Example 2, respectively. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] To address the problems in existing technologies where the elemental doping amount is affected by the surface morphology, hydrophilicity / hydrophobicity, internal or edge structure of the absorber layer during diffusion doping, resulting in uneven dopant distribution, poor process stability, and low doping activation rate, this invention provides an elemental doping method for the absorber layer of a thin-film solar cell, such as... Figure 1 As shown, the element doping method includes the following steps:

[0029] S10. Deposit a transparent conductive oxide layer on the substrate;

[0030] S20. An absorption layer is deposited on the transparent conductive oxide layer, and then an activation treatment is performed;

[0031] Optionally, before depositing the absorption layer, a high-resistivity transparent oxide layer can be deposited on the transparent conductive oxide layer first, and then the absorption layer can be deposited.

[0032] S30. Immerse the activated absorber layer in a salt solution containing a preset dopant element, heat it to a preset temperature, and simultaneously apply an exogenous inducing variable. After a preset time, the preset element doping is completed.

[0033] Optionally, the salt solution of the aforementioned pre-selected dopant element can be an aqueous solution or an organic solution, such as a methanol solution or an ethanol solution.

[0034] Alternatively, the above-mentioned deposition method can employ existing deposition methods, such as gas transport deposition, near-space sublimation deposition, etc.

[0035] Optionally, the above-mentioned method for activating the absorber layer can be achieved through chlorine doping and annealing. Specifically, cadmium chloride (CdCl2) or other chlorine-containing materials, including but not limited to MnCl2, MgCl2, NH4Cl, ZnCl2 or TeCl4, can be used. The annealing temperature is preset at 400℃~475℃, and the holding time is ≤60min. Through the synergistic effect of these process elements, the activation of the absorber layer is achieved.

[0036] It should be noted that the above activation treatment can effectively promote defect repair and crystal structure optimization within the absorption layer, thereby improving the photoelectric conversion performance of photovoltaic devices. It should be understood that the above element doping method is actually performed as a separate process step after the absorption layer deposition is completed. That is, the method involves removing the prepared absorption layer from the original deposition system, activating it, and then immersing it in a container holding a solution of a predetermined dopant element salt. The predetermined element is then doped by heating and simultaneously applying an exogenous inducing variable.

[0037] It should be noted that in the above-mentioned element doping method, by heating the salt solution of the dopant element and simultaneously applying an exogenous inducible variable, after a preset time, the preset dopant element can be made unaffected by the surface morphology, hydrophilicity / hydrophobicity, internal or edge structure of the absorption layer during the doping process. The specific mechanism for improving the uniformity of dopant element distribution, process stability and doping activation rate is as follows:

[0038] In the above element doping method, the concentration of the doping element source solution is uniform, constant and controllable, and the substrate sample containing the absorption layer is subjected to full liquid phase heating by the preset doping element salt solution. The heating temperature is uniform and without temperature difference, which can achieve uniform full-angle wetting and coverage of the preset doping element into the microstructure of the absorption layer surface, and is not affected by the morphology, hydrophilicity or hydrophobicity, internal or edge structure of the absorption layer.

[0039] Furthermore, as the heating temperature increases, the viscosity of the salt solution containing the preset element decreases, and the diffusion coefficient increases. This allows the ions of the preset dopant element to penetrate indiscriminately to the surface and grain boundary regions of the absorption layer, regardless of the surface morphology of the absorption layer. Secondly, after applying an external inducing variable, such as pressure, the mechanical stress generated by high pressure can cause micro-distortions in the lattice of the absorption layer, forming temporary ion channels. Combined with thermal activation at high temperature, this can increase the diffusion coefficient of the preset element ions and increase the chemical potential gradient of the dopant ions in the salt solution, which promotes the diffusion and doping of the preset element ions in the absorption layer. In addition, the increase in temperature can increase the kinetic energy of the dopant ions in the salt solution, overcoming the energy barriers on the surface and inside of the absorption layer. At the same time, the increase in temperature can accelerate the interfacial adsorption and ion exchange reactions between the dopant ions and the absorption layer matrix, changing the doping process from "passive diffusion" to "active reaction + diffusion," further reducing the doping differences in different regions of the absorption layer and achieving uniform doping of the preset element in the absorption layer.

[0040] In one possible implementation, the material of the absorber layer includes CdTe and CdSe. x Te 1-x and at least one of CdSe, wherein CdSe x Te 1-x The value of x ranges from 0% to 40%.

[0041] Optionally, when the value of x is in the range of 0% to 40%, CdSe x Te 1-x It can be CdSe 0.13 Te 0.87 CdSe 0.1 Te 0.9 or CdSe 0.2 Te 0.8 wait.

[0042] It should be noted that the aforementioned absorber layer can be directly formed by depositing a single material layer onto the photovoltaic device. For example, the deposited absorber layer material can be a single layer of CdTe or a single layer of CdSe. x Te 1-xIn this case, the elemental distribution within the material layer can be uniform; alternatively, a specific material gradient can be formed within the material layer, meaning that properties such as elemental concentration exhibit regular changes within the material layer. For example, when the absorption layer is a monolayer CdSe... x Te 1-x At that time, it can be CdSe with stable Se content. x Te 1-x A single layer, or CdSe with a gradual change in Se content. x Te 1-x In a single layer, the Se content preferably changes gradually upwards from the part near the TCO layer (including gradual increase, gradual decrease, increase followed by decrease, decrease followed by increase, or a gradual trend of increase, decrease, increase, decrease, etc., or a gradual trend of decrease followed by increase, decrease followed by increase, etc., all of which are included in the scope of this application); p-type doping of the absorption layer can increase the carrier concentration and effectively improve the electrical performance of the absorption layer.

[0043] In one possible implementation, the aforementioned exogenous induced variables include, but are not limited to, pressure, electric field, and magnetic field.

[0044] It should be understood that the aforementioned exogenous inducible variables refer to inducible variables actively applied outside the pre-defined element doping process of the aforementioned absorption layer. These variables can regulate the diffusion rate and distribution uniformity of the pre-defined dopant element during the doping process, without changing the physical or chemical parameters or forms of the inherent composition and crystal structure of the absorption layer substrate.

[0045] Optionally, the aforementioned exogenous inducing variables may also include ultrasonic fields, etc.

[0046] It should be noted that, in existing technologies, the ions of doped elements diffuse passively only through the concentration gradient, which is easily affected by the microstructure of the absorption layer, leading to problems such as uneven doping, low doping activation rate, and unstable process. The technical solution of this invention uses an exogenous inducible variable to assist in inducing ion movement. For example, when the exogenous inducible variable is pressure, applying a preset pressure can reduce the phenomenon of excessive doped ions being trapped in the micropores; simultaneously, it induces micro-distortion in the absorption layer lattice, forming temporary ion channels and improving ion diffusion characteristics. When the exogenous inducible variable is a magnetic field, if the doped ions are magnetic ions, or if paramagnetic components are present in the salt solution, the magnetic field can guide the ions along the path via the Lorentz force. The uniform movement of the magnetic field prevents ions from agglomerating due to uneven surface charge of the absorption layer. Non-magnetic ions can also achieve uniform ion distribution by driving solution convection through the magnetic field. When the exogenous inducible variable is an electric field, after applying a DC or AC electric field, the doped ions (positively or negatively charged) will migrate directionally along the direction of the electric field (electrophoresis), which can actively compensate for the ion concentration differences in different regions of the absorption layer. For example, applying a reverse electric field to the edge of the absorption layer (where ions are easily lost due to solution convection) can guide ions to migrate to the edge, avoiding the problem of "more doping in the center and less doping at the edge". At the same time, the electric field can suppress the distribution shift of ions caused by differences in diffusion coefficients (different diffusion rates in different regions).

[0047] Furthermore, when the aforementioned exogenous inducing variable is pressure, it can specifically solve the problem of excessive local doping elements caused by the internal pores of the absorption layer in the prior art; when the aforementioned exogenous inducing variable is a magnetic field, it can specifically solve the problem of ion aggregation caused by uneven surface charge of the absorption layer in the prior art; when the aforementioned exogenous inducing variable is an electric field, it can specifically solve the problems of ion concentration differences and uneven diffusion coefficients at the edge or center of the absorption layer in the prior art.

[0048] In one possible implementation, the salt solution of the aforementioned pre-selected dopant element may include at least one of Group I element salt solutions, Group V element salt solutions, and Group VII element salt solutions.

[0049] Optionally, when the preset dopant element is a Group V element, the salt solution can be a Group V element halide salt solution, carboxylate salt solution, β-diketone salt solution, or oxyanion salt solution, etc.

[0050] Optionally, when the above-mentioned group V element salt solution is a halide salt solution, the halide salt includes, but is not limited to, PF3, PCl3, PBr3, PI3, AsF3, AsCl3, AsBr3, AsI3, SbF3, SbCl3, SbBr3, SbI3, BiF3, BiCl3, BiBr3, or BiI3.

[0051] Optionally, when the above-mentioned group V element salt solution is a carboxylate solution, the carboxylate includes, but is not limited to, Bi salt, Sb salt, or K salt.

[0052] Optionally, when the above-mentioned Group V element salt solution is a Bi carboxylate salt solution, the Bi carboxylate salt includes, but is not limited to, Bi(CH3COO)3, Bi(C2H5COO)3, and Bi(C 10 H 19 O2)3、Bi(C7H 15 COO)3、Bi(C 17 H 33 COO)3、Bi(C 17 H 33 COO)3 or BiC6H5O7, etc.

[0053] Optionally, when the above-mentioned Group V element salt solution is a carboxylic acid Sb salt solution or a carboxylic acid K salt solution, the carboxylic acid Sb salt includes, but is not limited to, Sb(CH3COO)3 and Sb(C 10 H 19 O2)3 or Sb(C7H) 15 COO)3, and carboxylic acid K salts include, but are not limited to, K(SbO)C4H4O6, etc.

[0054] Optionally, when the above-mentioned group V element salt solution is a β-diketone salt solution, the β-diketone salt includes, but is not limited to, Sb(C5H7O2)3 or Bi(C5H7O2)3.

[0055] Optionally, when the above-mentioned Group V element salt solution is an oxyacid anion salt solution, the oxyacid anion salt includes, but is not limited to, Na[Sb(OH)6] or K[Sb(OH)6].

[0056] It should be understood that when the salt solution of the aforementioned preset doping element is a halide salt solution of a group V element, and when the halide salt solution is one of SbCl3, BiCl3, PCl3 and AsCl3, after doping the aforementioned absorption layer by the aforementioned element doping method, doping of a single group V element can be achieved. For example, doping of Sb, Bi, P or As elements can be achieved, thereby obtaining an absorption layer doped with a single group V element.

[0057] Furthermore, when the salt solution of the aforementioned preset doping element is a halide salt solution of a group V element, and when the halide salt solution includes at least two of SbCl3, BiCl3, PCl3, and AsCl3, after doping the aforementioned absorption layer using the aforementioned element doping method, multiple elements of group V can be doped simultaneously. For example, simultaneous doping of Sb and Bi elements, or simultaneous doping of Sb, Bi, and P elements, or simultaneous doping of Bi, P, and As elements, or simultaneous doping of Sb, Bi, P, and As elements can be achieved, thereby obtaining an absorption layer doped with multiple elements of group V.

[0058] It should be understood that, based on the above analysis of doping of Group V elements, when the salt solution of the preset dopant element is a Group I element salt solution or a Group VII element salt solution, or a mixed salt solution composed of any two or three of Group I, Group V, or Group VII element salt solutions, the above element doping method can achieve single-element doping or co-doping of multiple elements of Group I or Group VII; or can achieve co-doping of elements of any two or three of Group I, Group V, and Group VII.

[0059] It should be noted that when the salt solution of the aforementioned preset doping element is a Group I element salt solution, such as a Group IB element like Cu, Ag, or Au, the salt solution can be a Group IB element halide salt solution, nitrate solution, etc., which can achieve p-type doping. The specific doping mechanism may be as follows: When the above element doping method is used, when the above absorption layer is under the conditions of "salt solution heating immersion + exogenous inducible variable", for example, when the exogenous inducible variable is an electric field, the ions of Group I elements, such as Cu... 2+ It will break through the surface energy barrier of the absorption layer and diffuse into the interior of the CdTe or CdSe lattice, preferentially occupying the lattice sites of Cd atoms (Cd lattice sites), because Cu 2+ radius and Cd 2+ The proximity satisfies the lattice matching condition, allowing for stable substitution. Furthermore, when Cu replaces Cd, Cu can only provide one valence electron, while the original Cd atom needs to provide two valence electrons to form covalent bonds with the surrounding six group VI atoms (Te / Se). Therefore, when Cu replaces Cd, it will lack one valence electron, thus forming an acceptor defect energy level with energy far below the conduction band bottom and close to the valence band top. Moreover, the acceptor energy level will capture free electrons in the lattice to fill its own valence electron vacancy, while leaving electron vacancies in the valence band. These holes can move freely under the influence of electric field and temperature, thereby achieving p-type doping.

[0060] When the salt solution of the aforementioned pre-set dopant element is a Group V element salt solution, such as a salt solution of P, As, Sb, etc., p-type doping can be achieved when the above-mentioned element doping method is used. The specific doping mechanism may be, for example, when the Group V element ion is Sb... 3+ When the above-mentioned absorption layer is under the conditions of "salt solution heating and immersion + exogenous inducible variable", and when the exogenous inducible variable is pressure or magnetic field, Sb 3+ It can diffuse into the CdTe lattice and occupy the lattice sites of Te atoms, although Sb 3+ radius and Te 2- The differences are significant, but the crystal lattice of group V elements has a certain gap tolerance, and heating can increase lattice vibrations, thus enabling Sb to replace Te. Furthermore, when Sb replaces Te, since Sb can only provide 5 valence electrons, while the original Te atom needs to provide 6 valence electrons to form covalent bonds with the surrounding 3 Cd atoms, Sb will lack 1 valence electron, thus forming a shallow acceptor level. The shallow acceptor level will take an electron from the valence band to fill its own valence electron vacancy, resulting in a hole in the valence band. These holes become majority carriers, achieving p-type conduction.

[0061] When the salt solution of the aforementioned pre-selected dopant element is a Group VII element salt solution, such as F, Cl, Br, or I, the salt solution can be a halide, iodide, or bromide salt solution, such as CdCl2, KI, or Br2. When the above element doping method is used, p-type doping can be achieved. The specific doping mechanism may involve the use of Group VII element ions, such as Cl... - In salt solutions, through heating and electric field induction, it can diffuse into the CdTe lattice, thereby replacing Te. 2- , and Cl - radius and Te 2- The radii are close enough that they can stably occupy Te lattice sites, forming a high-valence substitution structure for a low-valence structure, becoming a shallow acceptor level, and releasing holes; while Cl - Its electronegativity is much higher than that of Te. 2- Cl doping can form Coulomb attraction with positively charged Cd interstitial atoms, suppressing the generation of Cd interstitial atoms and thus achieving p-type doping. At the same time, Cl doping can promote the formation of Cd vacancies, further enhancing p-type conductivity.

[0062] Optionally, the aforementioned preset doping element can be at least one of group I elements, group V elements, and group VII elements.

[0063] Alternatively, the aforementioned Group I elements can be Cu, Ag, Au, K, and Na.

[0064] Alternatively, the aforementioned group V elements can be N, As, P, Sb, and Bi.

[0065] Alternatively, the aforementioned group VII elements can be F, Cl, Br, and I.

[0066] It should be understood that when the salt solution containing the preset dopant element is a salt solution of a single element of Group I, such as Cu, the doping of Cu of Group I can be achieved according to the above-described element doping method; furthermore, when the salt solution is a salt solution of multiple elements of Group I, such as Cu and Ag, the co-doping of Cu and Ag of Group I can be achieved according to the above-described element doping method; and so on. It can be seen that according to the above-described element doping method of the present invention, the co-doping of a single element or multiple elements of Group V or Group VII can be achieved.

[0067] Furthermore, when the salt solution containing the preset dopant element includes any two or three elements from Group I, Group V, and Group VII, the above doping method can achieve simultaneous doping of any two elements from Group I, Group V, and Group VII. For example, when the salt solution containing the preset dopant element is a mixed salt solution of Cu and Sb, the above element doping method can achieve co-doping of Cu and Sb.

[0068] In one possible implementation, the above-mentioned element doping method has a preset temperature of 50℃~300℃, for example, 50℃, 100℃, 150℃, 200℃, 250℃ or 300℃; and a preset duration of ≤100min, for example, ≤90 min, ≤80 min, ≤50 min, ≤40 min, ≤20 min or ≤10 min.

[0069] Preferably, the preset temperature can be 150℃~220℃, for example, 150℃, 180℃, 200℃, 210℃ or 220℃.

[0070] Preferably, the preset duration can be 20 min to 40 min, for example, 20 min, 30 min or 40 min.

[0071] It should be noted that the above-described element doping method can achieve efficient diffusion and lattice occupancy of the preset dopant element in the absorption layer. Specifically, when the preset temperature is 50℃~300℃, for example, 150℃~220℃, and a certain pressure is applied, the ions of the preset dopant element, such as Sb, can diffuse efficiently. 3+ Bi 3+ It diffuses into the absorption layer through grain boundaries and lattice interstices, for example, into CdTe or CdSe. x Te 1-xInside the absorption layer, the doping depth can reach 2μm~3μm, which can cover the effective light absorption area of ​​the absorption layer, while avoiding excessive aggregation on the surface or insufficient internal doping.

[0072] It should be noted that by using the above element doping method, and by adjusting the time to a preset duration of ≤100 min, such as 20 min to 40 min, the carrier concentration and doping depth of the absorption layer can be controlled within an ideal range. In addition, a shorter duration, such as 20 min to 30 min, is suitable for low concentration and surface doping, while a longer duration, such as 30 min to 40 min, can increase the doping concentration and depth.

[0073] In the technical solution of this invention, by doping the absorption layer with preset elements, the carrier concentration can be significantly increased, while reducing scattering caused by impurity aggregation, thereby improving carrier mobility and laying the foundation for efficient transport of photogenerated carriers.

[0074] Optionally, when the above-mentioned exogenous inducing variable is pressure, the pressure can be 0.01MPa~5MPa, for example, 0.3MPa~1.0MPa.

[0075] It should be understood that when the pressure is between 0.01 MPa and 5 MPa, the solution can overcome surface tension, fully fill the micropores and grain boundaries on and inside the absorber layer, eliminate gas or liquid resistance at the interface, and allow doping elements, such as I, to... - Sb 3+ The contact area between the absorber and the absorber changes from local surface contact to three-dimensional contact, avoiding excessive or insufficient local doping caused by uneven wetting and improving doping uniformity.

[0076] Optionally, when the above-mentioned exogenous induced variable is an electric field, the strength of the electric field can be 1 V / m to 100 kV / m, for example, it can be 1 V / m, 50 V / m, 100 V / m or 1000 V / m, etc.

[0077] It should be understood that when the electric field strength is between 1 V / m and 100 kV / m, if the doping ion is an anion, such as Group VII ions like I⁻ and Cl⁻, it will migrate towards the anode of the electric field; if it is a cation, such as Sb... 3+ As 3+ Group V ions migrate towards the cathode; this directional migration can overcome the limitations of the concentration gradient, forcing ions to uniformly penetrate into the micropores, grain boundaries and grain interior of the absorption layer. Especially for thicker CdTe absorption layers, such as >2 μm, it can effectively avoid the gradient defect of surface doping saturation and deep undoped layers, and achieve effective doping across the entire thickness range.

[0078] Furthermore, the electric field polarizes the lattice atoms on the surface of the absorption layer, such as Cd. 2+ Te 2- This enhances the electrostatic attraction of charged doped ions, allowing them to adsorb onto the surface more quickly and form stable adsorption states. When the electric field strength is low, such as 1 V / m to 100 V / m, the ion migration rate is moderate, suitable for low concentration and shallow doping, such as slight doping on the surface of the absorber layer, to modulate the surface barrier; when the electric field strength is high, such as 500 V / m to 1000 V / m, the ion migration rate is accelerated, enabling high concentration and deep doping.

[0079] Optionally, when the aforementioned exogenous inducible variable is a magnetic field, the strength of the magnetic field is 1 G to 10000 G. For example, a magnetic field with a lower intensity range can be selected, such as 1 G to 10 G, 1 G to 30 G, or 31 G to 50 G. A magnetic field with a medium intensity range can also be selected, such as 100 G to 200 G, 210 G to 400 G, or 410 G to 600 G. A magnetic field with a higher intensity range can also be selected, such as 610 G to 700 G, 710 G to 800 G, or 810 G to 10000 G.

[0080] It should be noted that when the magnetic field strength is 1 G to 10000 G, mild convection can be formed in the weak magnetic field range of 1 G to 100 G, which is suitable for surface-sensitive absorption layers, such as thin CdSe layers, to avoid strong convection damaging the surface structure. The medium-strong magnetic field of 100 G to 10000 G can enhance the convection intensity. For thick CdTe absorption layers, such as 2 μm to 5 μm, it can effectively solve the problem of insufficient deep doping and reduce the deviation of doping concentration across the entire thickness range.

[0081] In one possible implementation, the above-mentioned element doping method further includes heat treatment of the absorber layer that has undergone exogenous induced immersion liquid phase pre-doped element treatment, wherein the heat treatment temperature is ≤400℃ and the duration is ≤60min.

[0082] Optionally, the temperature of the heat treatment can be 250℃~300℃, for example, 250℃, 280℃, or 300℃; the duration can be 8min~15min.

[0083] Alternatively, the above heat treatment method can be:

[0084] The absorption layer doped with the preset elements is placed in a heating furnace, and its temperature is adjusted to ≤400℃. Then, it is kept at the temperature for ≤60 minutes, and then cooled to room temperature to complete the heat treatment.

[0085] In the above heat treatment, the temperature range of ≤400℃ can promote the volatilization and removal of residual dopant source solution on the surface of the absorption layer, and at the same time effectively suppress the pyrolysis and volatilization of volatile components in the absorption layer itself, thus avoiding the imbalance of the stoichiometry of the absorption layer.

[0086] In one possible implementation, when the salt solution of the aforementioned preset dopant element is a salt solution of a group V element, the concentration of the salt solution can be 0.01 mmol / L to 10 mmol / L, for example, 0.05 mmol / L to 0.1 mmol / L.

[0087] It should be noted that when the concentration of the group V element halide salt solution is between 0.01 mmol and 10 mmol, excessive deposition of group V elements on the absorber surface due to excessive salt solution concentration can be avoided, while ensuring the presence of doped ions, such as Sb. 3+ Bi 3+ By diffusing and distributing evenly within the absorber layer, the uneven distribution problem of "surface enrichment" and "internal depletion" is avoided; secondly, when the halide salt solution is a mixed salt solution, such as a mixture of SbCl3 and BiCl3, because Sb... 3+ Its diffusion coefficient is slightly higher than that of Bi. 3+ This can make Sb 3+ It mainly diffuses into the deeper layers of the absorption layer, thereby providing bulk carriers, while Bi 3+ It can be more concentrated near the surface and grain boundaries, thereby suppressing surface recombination, forming "gradient doping", and ultimately optimizing the longitudinal electric field distribution.

[0088] Furthermore, under the aforementioned low concentration conditions of 0.01 mmol / L to 0.1 mmol / L, the deep-level defects formed by the aggregation of Group V elements, such as the Sb₂Te₃ or Bi₂Te₃ precipitation phase problem, can be reduced. The synergistic effect of Sb and Bi can mutually passivate shallow-level defects that the other may introduce, such as Sb… 3+ Or Bi 3+ Inverted defects improve carrier lifetime and mobility.

[0089] Optionally, when the salt solution of the preset doped element is a salt solution of a Group I element, the concentration of the salt solution is 0.01 mmol / L to 10 mmol / L.

[0090] It should be noted that if the concentration of the aforementioned Group I element salt solution is too low, for example, <0.01 mmol / L, the doping amount of Group I element ions on the surface / bulk of the absorber layer is insufficient, resulting in a low acceptor level density. This makes it difficult to effectively compensate for the intrinsic n-type defects of the material (such as Cd vacancies and Te interstitial atoms), making it difficult to achieve stable p-type conductivity. If the concentration is too high, for example, >10 mmol / L, excess Group I ions tend to accumulate in the interlattice to form "deep level traps," which reduces carrier mobility. However, when the concentration is between 0.01 mmol / L and 10 mmol / L, the ions can diffuse into the absorber layer through diffusion, while avoiding the problem of local overdoping caused by excessively high ion concentrations. Furthermore, the ionic radii of Group I elements (Na, K, etc.) are similar to those of Cd... 2+ Low-concentration doping can minimize lattice distortion, reduce defect density, and improve the crystal quality of semiconductor materials.

[0091] Optionally, when the salt solution of the preset doped element is a salt solution of a group VII element, the concentration of the salt solution is 0.01 mmol / L to 0.1 mmol / L.

[0092] It should be noted that when the concentration of the above-mentioned Group VII element salt solution is 0.01 mmol to 0.1 mmol, the doping concentration of Group VII element ions in the absorber layer is stable and controllable. If the concentration is too high, for example, >0.1 mmol, it will lead to excessive accumulation of Group VII element ions at the grain boundaries, or react with cations in the absorber layer, such as Cd. 2+ The formation of deep-level impurity complexes leads to the trapping of free electrons by the trapped states, which in turn reduces carrier mobility.

[0093] To address the problems of low carrier concentration, short lifespan, and long-term instability in the absorption layer of existing thin-film solar cells, this invention also provides a thin-film solar cell comprising a substrate, a transparent conductive oxide layer, an absorption layer, a back contact layer, and a back electrode layer, wherein the absorption layer is elementally doped using the aforementioned elemental doping method.

[0094] In one possible implementation, the aforementioned thin-film solar cell further includes an antireflection film, a sodium-blocking layer, a high-resistivity layer, and a passivation layer. The antireflection film is disposed on one side of the substrate, the sodium-blocking layer is deposited on the substrate, the high-resistivity layer is deposited on the transparent conductive oxide layer, and the passivation layer is deposited on the absorption layer and / or the back contact layer.

[0095] It should be noted that the absorber layer of the aforementioned thin-film solar cell is doped with preset elements using the aforementioned element doping method. Specifically, through an immersion liquid-phase doping process with an externally induced variable, the ions of the dopant element can be directionally driven into the absorber layer lattice. Combined with low-temperature heat treatment to promote the ionization of the dopant element, the effective carrier concentration is significantly increased, solving the problem of low carrier concentration in the absorber layer in the prior art. Secondly, salt solution doping avoids lattice damage caused by high-energy particle injection. At the same time, the externally induced variable can reduce the recombination centers formed by the agglomeration of dopant elements, and the low-temperature heat treatment repairs lattice defects. In addition, when the induced variable is an electric field, the gradient carrier distribution formed by the partitioned doping can suppress the accumulation of carriers at the grain boundaries and reduce non-radiative recombination. Ultimately, this improves the carrier lifetime, increases the transport distance of photogenerated carriers, and enhances the photoelectric conversion efficiency of the cell.

[0096] Example 1

[0097] A method for element doping of the absorber layer of a thin-film solar cell includes the following steps:

[0098] S10. A transparent conductive oxide layer FTO of approximately 450 nm is deposited on a glass substrate using chemical vapor deposition; then a high-resistivity transparent oxide layer SnO2 of approximately 40 nm is deposited.

[0099] S20. Deposit CdSe on the high-resistivity transparent conductive oxide layer 0.13 Te 0.87 The absorbent layer is then placed in a tubular furnace and heated to 450°C in a CdCl2 atmosphere. The furnace is held at that temperature for 15 minutes and then cooled to room temperature to complete the activation process.

[0100] S30. Activated CdSe 0.13 Te 0.87 The absorber layer was immersed in a 0.01 mmol / L SbCl3 methanol solution, heated to 150 °C, and subjected to a pressure of 0.3 MPa. After 40 min, Sb doping was completed, yielding Sb-doped CdSe. 0.13 Te 0.87 Absorption layer.

[0101] S40. S30 yields CdSe doped with Sb. 0.13 Te 0.87 The absorption layer undergoes heat treatment, specifically as follows:

[0102] CdSe doped with Sb 0.13 Te 0.87 The absorption layer is placed in a heating furnace, heated to 240°C, held for 15 minutes, and then cooled to room temperature to complete the heat treatment.

[0103] Comparative Example 1 is set up under Example 1.

[0104] In Comparative Example 1, S10, S20 and S40 are the same as in Example 1.

[0105] The difference between Comparative Example 1 and Example 1 is that in S30: a 0.01 mmol / L SbCl3 methanol solution is spin-coated onto the activated CdSe. 0.13 Te 0.87 Surface of the absorption layer.

[0106] CdSe doped with Sb obtained in Example 1 and Comparative Example 1 respectively 0.13 Te 0.87 The absorber layer is applied in thin-film solar cells to obtain two types of thin-film solar cells, both of which include a substrate, a transparent conductive oxide layer, a high-resistivity layer, an absorber layer, a back contact layer, and a back electrode layer.

[0107] At AM1.5, 100 mW / cm 2 The performance of these two thin-film solar cells was tested under standard test conditions of illumination and 25°C, and the results are as follows: Figure 2 As shown.

[0108] like Figure 2 The graph shows the current density-voltage (JV) characteristic curve of a thin-film solar cell. From the graph, we can see that:

[0109] First, the open-circuit voltage of the thin-film solar cell in Example 1 is 876 mV, while that of Comparative Example 1 is 837 mV. This indicates that the absorber layer of the thin-film solar cell in Example 1 has undergone more effective p-type doping, which significantly increases the built-in potential and suppresses the recombination loss of carriers related to defects caused by doping.

[0110] Secondly, the short-circuit current density in Example 1 is 29.7 mA / cm². 2 The value for Comparative Example 1 was 28.7 mA / cm². 2 This indicates that the thin-film solar cell obtained in Example 1 can generate more photogenerated carriers and has stronger light absorption and carrier collection capabilities.

[0111] Furthermore, the fill factor of the thin-film solar cell in Example 1 is 78.9% and the photoelectric conversion efficiency is 20.4%, while the fill factor of Comparative Example 1 is 70.5% and the photoelectric conversion efficiency is 16.9%. This indicates that the thin-film solar cell in Example 1 has less power loss and better photoelectric conversion performance.

[0112] According to Figure 2Analysis shows that in the technical solution of the present invention, the purpose of element doping of the absorption layer is achieved by immersion liquid phase doping and simultaneous application of exogenous induced variables. At the same time, the electrical characteristics such as carrier concentration and mobility of the absorption layer can be better adjusted, thereby improving the photoelectric conversion efficiency of thin-film solar cells.

[0113] Example 2

[0114] A method for element doping of the absorber layer of a thin-film solar cell, wherein steps S10 and S20 are the same as in Example 1.

[0115] S30. Activated CdSe 0.2 Te 0.8 The absorber layer was immersed in a 0.05 mmol methanol solution containing SbCl3 and BiCl3 in a 1:1 molar ratio. The solution was heated to 150 °C and subjected to a pressure of 0.3 MPa. After 40 minutes, Sb and Bi doping was completed, yielding CdSe doped with Sb and Bi. 0.2 Te 0.8 Absorption layer.

[0116] The absorber layer obtained through steps S10 to S30 is applied to a thin-film solar cell to obtain a thin-film solar cell. The thin-film solar cell may include a substrate, a transparent conductive oxide layer, a high-resistivity layer, an absorber layer, a back contact layer, and a back electrode layer. If an antireflection film, a sodium-blocking layer, and a back contact passivation layer are deposited during the cell fabrication process, then the thin-film solar cell includes an antireflection film, a substrate, a sodium-blocking layer, a transparent conductive oxide layer, a high-resistivity layer, an absorber layer, a back contact passivation layer, and a back electrode layer.

[0117] Comparative Example 2 is set up under Example 2.

[0118] In Comparative Example 2, S10, S20, and S30 are the same as in Example 2.

[0119] The difference between Comparative Example 2 and Example 2 is that the absorber layer doped with Sb and Bi elements obtained after S30 is subjected to heat treatment. Specifically, the absorber layer doped with Sb and Bi elements is placed in a heating furnace, heated to 300°C, and held for 15 minutes to complete the heat treatment.

[0120] SIMS measurements were performed on the dopant element distribution of the absorber layers doped with Sb and Bi elements obtained in Example 2 and Comparative Example 2, respectively. The results are as follows: Figure 3 As shown.

[0121] Figure 3Neutron diagram a shows the distribution of Sb and Bi elements in the absorption layer of Example 2; sub-diagram b shows the distribution of Sb and Bi elements in the absorption layer of Comparative Example 2. Comparative analysis of sub-diagrams a and b shows that before heat treatment, the distribution of Sb elements in the absorption layer is relatively dispersed and uniform, without obvious aggregation or regular distribution characteristics. After heat treatment, the distribution of Sb elements does not change significantly. Before heat treatment, the distribution of Bi elements in the absorption layer is relatively sparse but relatively uniform. After heat treatment, the distribution of Bi elements does not change significantly.

[0122] According to Figure 3 Analysis shows that in the technical solution of the present invention, by using immersion liquid-phase doping and applying a single exogenous inducing variable, both the diffusion and depth distribution of the dopant element can be achieved. Furthermore, heat treatment of the absorbed layer after doping does not significantly affect the doping depth or distribution of the dopant element. This indicates that the technical solution of the present invention, by employing an element doping method that combines immersion liquid-phase doping with the application of an exogenous inducing variable, can promote the diffusion and doping of ions of the preset dopant element into the grain boundaries and lattice interior of the absorbed layer, with minimal dependence on the subsequent heat treatment process to promote ion diffusion and doping.

[0123] Example 3

[0124] A method for element doping of the absorber layer of a thin-film solar cell includes the following steps:

[0125] S10. A transparent conductive oxide layer FTO of approximately 450 nm is deposited on a glass substrate using chemical vapor deposition; then a high-resistivity transparent oxide layer ZnO of approximately 30 nm is deposited.

[0126] S20. Deposit CdSe on the transparent conductive oxide layer 0.2 Te 0.8 The absorption layer is then placed in a heating furnace. Under a CdCl2 atmosphere, the furnace is heated to 450°C and held for 14 minutes. The furnace is then cooled to room temperature to complete the activation process.

[0127] S30. The activated CdTe absorber layer is immersed in a methanol solution composed of SbCl3, Cu(NO3)2 and CdCl2, wherein the molar ratio of SbCl3, Cu(NO3)2 and CdCl2 is 4:1:1. The temperature is raised to 220℃ and an electric field of 15V / cm is applied. After 20min, the co-doping of Sb, Cu and Cl elements is completed, and an absorber layer doped with Sb, Cu and Cl elements is obtained.

[0128] In this doping method, firstly, Sb, as a group V element, is doped into CdSe. 0.2Te 0.8 The Sb atom replaces the Te (group VI) lattice position in the crystal lattice of a group II-VI compound. Te atoms typically form a stable hexavalent structure in the lattice, while Sb atoms have only five valence electrons. Replacing Te with Sb results in one less electron, forming an acceptor level (i.e., a hole trap). This acceptor level can trap nearby electrons, creating free holes in the crystal and contributing to p-type conductivity. Simultaneously, an electric field of 15 V / cm can promote Sb conductivity. 3+ Ions migrate directionally to the surface of the absorption layer in methanol solution, enhancing their diffusion ability in the crystal lattice, improving the doping efficiency and uniformity of Sb, and strengthening the p-type conductivity.

[0129] Secondly, Cu, as a Group I element, is present in CdSe. 0.2 Te 0.8 Cu can replace Cd (Group II) lattice sites in the crystal lattice. Cd atoms are divalent, while Cu atoms are monovalent. After substitution, Cu will lose one valence electron, forming an acceptor defect. This acceptor defect will accept electrons and generate holes, directly enhancing the p-type conductivity. Because the atomic radius of Cu is closer to that of Cd, Cu can more easily and stably occupy Cd lattice sites. Moreover, Cu's acceptor energy level is shallower (closer to the top of the valence band), and its hole ionization energy is low, which can effectively increase the hole concentration, thereby achieving p-type doping.

[0130] Furthermore, as a group VII element, Cl may substitute for Te in the crystal lattice; because Cl... - radius and Te 2- The radii are close enough that they can stably occupy Te lattice sites, forming a high-valence substitution structure for a low-valence structure, becoming a shallow acceptor level, and releasing holes; while Cl - Its electronegativity is much higher than that of Te. 2- CdCl2 can form Coulomb attraction with positively charged Cd interstitial atoms, inhibiting the formation of Cd interstitial atoms and potentially achieving p-type doping. Furthermore, in a mixed system of SbCl3, Cu(NO3)2, and CdCl2, CdCl2 can modulate the ionic strength and chemical environment of the solution, forming a relatively stable ionic environment with SbCl3 and Cu(NO3)2, thus promoting Sb... 3+ Cu 2+ Uniform dispersion of ions avoids ion aggregation, indirectly improving the uniformity and stability of p-type doping.

[0131] By applying an absorber layer doped with Sb, Cu, and I elements to a thin-film solar cell, a thin-film solar cell is obtained. The thin-film solar cell may include a substrate, a transparent conductive oxide layer, a high-resistivity layer, an absorber layer, a back contact layer, and a back electrode layer.

[0132] Example 4

[0133] A method for element doping of the absorber layer of a thin-film solar cell includes the following steps:

[0134] S10. A transparent conductive oxide layer FTO of approximately 450 nm is deposited on a glass substrate using chemical vapor deposition; then a high-resistivity transparent oxide layer ZnO of approximately 30 nm is deposited.

[0135] S20. Deposit CdSe and CdTe absorption layers on the transparent conductive oxide layer, then place the deposited layer in a heating furnace, heat the furnace to 420°C in a CdCl2 atmosphere, hold for 15 minutes, and then cool to room temperature to complete the activation treatment.

[0136] S30. The activated CdSe / CdTe absorber layer is immersed in a methanol solution composed of SbCl3, As(NO3)3, and CdCl2, wherein the molar ratio of SbCl3, As(NO3)3, and CdCl2 is 2:3:1. The temperature is raised to 300℃, the solution is stirred and a magnetic field of 100G is applied. After 30 minutes, the co-doping of Sb, As, and Cl elements is completed, and an absorber layer doped with Sb, As, and Cl elements is obtained.

[0137] In this doping method, Sb in SbCl3, As(NO3)3, and CdCl2 3+ As 3+ Cl - By replacing Cd in the CdSe / CdTe absorber layer 2+ Te 2- or Se 2- This achieves p-type doping.

[0138] By applying an absorber layer doped with Sb, As, and Cl elements to a thin-film solar cell, a thin-film solar cell is obtained. This thin-film solar cell may include a substrate, a transparent conductive oxide layer, a high-resistivity layer, an absorber layer, a back contact layer, and a back electrode layer.

[0139] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for elemental doping of the absorber layer of a thin-film solar cell, characterized in that, The element doping method is an exogenously induced immersion liquid phase doping method, which includes the following steps: The activated absorber layer is immersed in a salt solution containing a preset dopant element, heated to a preset temperature, and an exogenous inducing variable is applied. After a preset time, the doping of the preset element is completed. The absorber layer is made of CdTe or CdSe. x Te 1-x and at least one of CdSe, wherein CdSe x Te 1-x The value of x in the range is 0% to 40%; The salt solution of the preset doping element includes at least one of Group I element salt solution, Group V element salt solution and Group VII element salt solution; The concentration of the Group I element salt solution is 0.01 mmol to 10 mmol; the concentration of the Group V element salt solution is 0.01 mmol to 10 mmol; and the concentration of the Group VII element salt solution is 0.01 mmol to 0.1 mol.

2. The elemental doping method of claim 1, wherein, The exogenous induced variables include at least one of pressure, electric field, and magnetic field.

3. The elemental doping method of claim 1, wherein, The preset temperature is 50℃~300℃, and the preset duration is ≤100min.

4. The method of claim 2, wherein the element doping method is characterized by, When the exogenous induced variable is pressure, the pressure is 0.01MPa~5MPa; when the exogenous induced variable is electric field, the electric field is 1V / m~100kV / m; when the exogenous induced variable is magnetic field, the magnetic field is 1G~10000G.

5. The elemental doping method of claim 1, wherein The element doping method further includes heat treatment of the absorber layer that has undergone preset element doping, wherein the heat treatment temperature is ≤400℃ and the duration is ≤60min.

6. A thin-film solar cell, characterized by comprising: The thin-film solar cell includes a substrate, a transparent conductive oxide layer, an absorber layer, a back contact layer, and a back electrode layer. The absorber layer is doped with elements after activation treatment, and the method of element doping is as described in any one of claims 1 to 5.

7. The thin-film solar cell according to claim 6, characterized in that, The thin-film solar cell further includes an antireflection film, a sodium-blocking layer, a high-resistivity layer, and a passivation layer. The antireflection film is disposed on one side of the substrate, the sodium-blocking layer is deposited on the substrate, the high-resistivity layer is deposited on the transparent conductive oxide layer, and the passivation layer is deposited on the absorption layer and / or the back contact layer.

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