A passivated antimony selenide thin film solar cell

Abstract

The application discloses a kind of passivated antimony selenide (Sb2Se3) thin film solar cell and preparation method, the cell from bottom to top includes in turn: indium tin oxide (ITO) transparent conductive glass front electrode substrate, cadmium sulfide (CdS) electron transport layer, Sb2Se3 absorption layer, polyvinylidene fluoride-trifluoroethylene copolymer P (VDF-TrFE) passivation layer and gold (Au) back electrode layer.The passivated antimony selenide (Sb2Se3) thin film is P (VDF-TrFE) thin film in Sb2Se3 absorption layer surface spin coating, and the surface deep level defect of passivation film is passivated.The advantages of the application are that the scientific problem that Sb2Se3 semiconductor thin film surface deep level defect causes Sb2Se3 solar cell open-circuit voltage to be low is successfully solved by P (VDF-TrFE) thin film strategy, so as to improve the performance of Sb2Se3 thin film solar cell.This innovative technology provides an important technical solution for preparing high-efficiency and low-cost Sb2Se3 thin film solar cell.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor materials and thin-film solar cells, and particularly relates to a surface passivation technology for enhancing the photoelectric conversion efficiency of a Sb2Se3 thin-film solar cell by using an absorption layer thin film and a detailed preparation process thereof. BACKGROUND

[0002] In the field of photovoltaics, Sb2Se3 has become a P-type semiconductor material that attracts much attention due to its excellent light absorption capacity (as high as 10 5 cm -1 ) and flexible band gap adjustment (1.1-1.7 eV). Its theoretical efficiency can exceed 30%, and, in addition to a low crystal growth temperature and good environmental compatibility, Sb2Se3 brings revolutionary prospects for solar absorption layer materials. It is environmentally robust and can resist the erosion of moisture and oxygen, expanding its scientific and commercial application potential. At present, the optimization of Sb2Se3 thin-film solar cells urgently needs to solve the problem of deep level defects on the surface of the absorption layer, which significantly increases the carrier recombination loss and limits the photoelectric performance of the cell. Carrying out research on the control of surface defects is the key to achieving a breakthrough in the performance of Sb2Se3 thin-film solar cells. SUMMARY

[0003] In view of the serious recombination of carriers by deep level defects on the surface of the absorption layer and the resulting limited efficiency of Sb2Se3 thin-film solar cells, the purpose of the present application is to provide a Sb2Se3 thin-film solar cell with surface passivation of the absorption layer. The solution is to apply a polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) thin film to the surface of the Sb2Se3 absorption layer using a spin coating technique, effectively achieving passivation of the absorption layer. By adjusting the molar ratio of VDF to TrFE in P(VDF-TrFE), the present application not only reduces the recombination loss on the surface of the Sb2Se3 absorption layer, but also improves the performance of the passivation layer, increases the transport efficiency of the carriers, solves the core problem of low open-circuit voltage, and significantly improves the efficiency of the Sb2Se3 thin-film solar cell, thereby providing a new passivation structure and passivation process for the preparation of high-efficiency Sb2Se3 thin-film solar cells.

[0004] The specific technical scheme to achieve the purpose of the present application is as follows:

[0005] A passivated antimony selenide Sb2Se3 thin-film solar cell, characterized in that the cell comprises, from bottom to top, an indium tin oxide ITO transparent conductive glass front electrode substrate, an electron transport layer, an absorption layer, a passivation layer, and a back electrode layer.

[0006] The electron transport layer is a cadmium sulfide CdS thin film with a thickness of 20-150 nm.

[0007] The absorption layer is an antimony selenide (Sb₂Se₃) thin film with a thickness of 200–2000 nm;

[0008] The passivation layer is a polyvinylidene fluoride-trifluoroethylene copolymer P(VDF-TrFE) film with a thickness of 10-150 nm;

[0009] The back electrode layer is a gold (Au) electrode thin film with a thickness of 50–150 nm;

[0010] The passivated antimony selenide (Sb2Se3) film is prepared by spin-coating a polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) film onto the surface of the Sb2Se3 absorber layer, thereby passivating deep-level defects on the film surface. The polyvinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) film eliminates the low open-circuit voltage caused by deep-level defects on the surface of the Sb2Se3 semiconductor film.

[0011] A method for fabricating the aforementioned passivated antimony selenide (Sb₂Se₃) thin-film solar cell involves first cleaning an ITO glass substrate, then sequentially depositing an electron transport layer and an absorber layer using techniques such as chemical bath deposition and thermal evaporation. Subsequently, a spin-coating process is used to form P(VDF-TrFE) passivation layers with different VDF / TrFE molar ratios. During this process, the spin-coating speed, time, and concentration of the P(VDF-TrFE) solution are adjusted to optimize the passivation effect. Finally, a gold electrode layer is formed using techniques such as thermal evaporation, completing the fabrication of the solar cell. This method allows for precise control of the thickness and uniformity of each layer, thereby enabling the manufacture of high-performance Sb₂Se₃ thin-film solar cells. The specific steps include:

[0012] 1) Cleaning of the front electrode substrate of indium tin oxide (ITO) transparent conductive glass: First, clean with a solution containing detergent, then perform continuous ultrasonic cleaning with acetone and ethanol, and finally rinse with deionized water and purge with high-purity nitrogen until dry for later use.

[0013] 2) Preparation of the electron transport layer CdS thin film: A CdS thin film was deposited on the substrate in step 1) using a chemical water bath method. The CdS thin film was then spin-coated with a 20 mg / ml CdCl2 ethanol solution at a spin speed of 2000 r / s for 30 s. Subsequently, it was annealed at a temperature of 350–450 °C for 5 min to form an electron transport layer with a thickness controlled between 20 and 150 nm.

[0014] 3) Preparation of the Sb2Se3 thin film as the absorbing layer, which is deposited on the CdS thin film by vapor transport method; during the process, the temperature is raised at a rate of 20-100 °C / min, and the temperature is raised to 450-550 °C, and then the temperature is kept at 2.5-3.5 Pa for 2-5 min, and then naturally cooled to room temperature; the obtained Sb2Se3 thin film is used as the absorbing layer, and the thickness is 200-2000 nm;

[0015] 4) Preparation of the P(VDF-TrFE) thin film as the passivation layer, first, a solution of 2-10 wt% of the copolymer P(VDF-TrFE) is prepared, and diethyl carbonate is used as the solvent; the solution is spin-coated on the surface of the Sb2Se3 thin film, and during the spin-coating, the speed is first kept at 300-1000 r / s for 5-10 s, and then the speed is increased to 2000-4000 r / s for 10-25 s; during the drying process, the temperature is first kept at 90-120 °C for 10-60 min to promote the evaporation of the solvent, and then the temperature is kept at 135-165 °C for 2-8 hours to improve the crystallinity of the thin film, and a P(VDF-TrFE) thin film with a thickness of 10-150 nm is formed, which is the passivation layer;

[0016] 5) Preparation of the Au thin film as the back electrode layer, which is deposited on the P(VDF-TrFE) thin film by thermal evaporation method under vacuum condition, and the thickness is controlled at 50-150 nm, and the preparation of the Sb2Se3 thin film solar cell with the passivation layer is completed

[0017] Step 4) The P(VDF-TrFE) thin film as the passivation layer can also be prepared according to the following steps:

[0018] a) The P(VDF-TrFE) is dissolved in diethyl carbonate at a ratio of 2-10 wt%, and heated in a water bath at 60 °C for 4 hours to accelerate the dissolution of the solute;

[0019] b) The obtained solution is added dropwise to the surface of the Sb2Se3 thin film, and a thin film is formed by spin-coating; the spin-coating process includes two stages: first, spin-coating at a speed of 300-1000 r / s for 6-8 s, and then increasing the speed to 2000-4000 r / s for 15-20 s;

[0020] c) placing the sample coated with the thin film in an environment of 100-110°C for 20-40 min to promote solvent evaporation; then, under the same conditions, spin-coating a second layer of polyvinylidene fluoride-trifluoroethylene copolymer P(VDF-TrFE) solution; repeating this process until the polyvinylidene fluoride-trifluoroethylene copolymer P(VDF-TrFE) thin film of the desired thickness is obtained by spin-coating different times, the thickness being 10-150 nm;

[0021] d) placing the sample coated with the polyvinylidene fluoride-trifluoroethylene copolymer P(VDF-TrFE) in an environment of 140-160°C for 3-7 hours; completing the preparation of the passivation layer.

[0022] Compared with the conventional technology, the present application effectively optimizes the energy level arrangement of the interface of the back electrode of the solar cell by precisely controlling the VDF / TrFE molar ratio of the P(VDF-TrFE) passivation layer. This strategy significantly reduces the recombination loss at the interface, solves the problem of the decrease of the open-circuit voltage caused by the deep energy level defects on the surface of the Sb2Se3 semiconductor material, and suppresses the recombination of the carriers at the deep defects, thereby improving the charge collection efficiency. On the basis of the conventional glass / ITO / CdS / Sb2Se3 / Au structure, by introducing P(VDF-TrFE) as a passivation layer, the present application not only simplifies the preparation process, but also significantly improves the efficiency of the solar cell device, paving the way for the production of high-efficiency and low-cost Sb2Se3 thin film solar cells. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The figure is a schematic diagram of the P(VDF-TrFE) passivated Sb2Se3 thin film solar cell structure of the present application;

[0024] Figure 2 The figure is the XRD pattern of the Sb2Se3 thin film after P(VDF-TrFE) passivation of Example 1 of the present application and the unpassivated Sb2Se3 thin film of Comparative Example 1;

[0025] Figure 3 The figure is the scanning electron microscope image of the Sb2Se3 thin film after P(VDF-TrFE) passivation of Example 1 of the present application and the unpassivated Sb2Se3 thin film of Comparative Example 1;

[0026] Figure 4 The figure is the J-V curve of the Sb2Se3 thin film solar cell of Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0027] The present detailed description describes a method for preparing a Sb2Se3 thin film solar cell on a transparent ITO conductive glass substrate. As shown in the figure, Figure 1As shown, the solar cell structure includes several key layers: electron transport layer, absorber layer, passivation layer and electrode layer. On the transparent ITO conductive glass substrate 5, first deposit the electron transport layer 4 CdS thin film, thickness in 20-150 nm, to ensure the effective injection and transport of electrons. Then deposit the absorber layer 3 Sb2Se3 thin film, thickness in 200-1500 nm, responsible for the absorption of incident photons and photoelectric conversion. Subsequently, the passivation layer 2 is implemented, which is composed of P(VDF-TrFE) material, thickness of 10-150 nm, passivation effect is to reduce the recombination of surface carriers, improve the conversion efficiency of the battery device. Finally, deposit the Au electrode layer 1 on the passivation layer, thickness of 50-150 nm, as the back electrode of the battery device.

[0028] The solar cell is prepared by the following steps:

[0029] 1) Pretreatment of the substrate: First, a solution containing detergent is applied, followed by the application of acetone and ethanol, each step accompanied by ultrasonic assistance. Finally, deionized water is used for the final rinse, and the entire substrate is dried under a nitrogen stream for subsequent use.

[0030] 2) Formation of the electron transport layer: On the clean ITO substrate, the CdS thin film is formed by chemical water bath deposition method. Specifically, a 20 mg / ml CdCl2 solution is prepared in ethanol and applied to the substrate surface, followed by spin coating on a spin coater at a speed of 2000 r / s for 30 s. Then, in an air atmosphere, the CdS thin film is subjected to heat treatment at 350-450°C to obtain the ideal crystal structure and electron transport properties.

[0031] 3) Deposition of the absorber layer: For the deposition of the Sb2Se3 thin film, a vapor transport device is used to form a uniform and continuous absorber layer on the CdS layer. Under controlled conditions, including a gas pressure of 2.5-3.5 Pa and heating to 450-550°C at a rate of 20-100°C / min, holding for 3 min, and then allowing the film to cool naturally to ambient temperature.

[0032] 4) Spin coating of the passivation layer: To reduce interface defects and improve device performance, a 2-10 wt% P(VDF-TrFE) nanoparticle solution is spin coated on the surface of the Sb2Se3 thin film. After spin coating, the sample is subjected to heat treatment to evaporate the solvent, forming a uniform passivation layer.

[0033] 5) Deposition of the electrode layer: In a highly controlled vacuum environment, the gold electrode layer is precisely deposited on the passivation layer by thermal evaporation technology. The thickness of the electrode is adjusted between 80-120 nm to ensure good conductivity and the performance of the final battery device.

[0034] Sb2Se3 powder (99.999% purity) used in the preparation of the Sb2Se3 thin film in step 3).

[0035] The present application is further described in conjunction with the following specific examples, which are not intended to limit the scope of the application. Any variations and modifications of the examples that occur to those skilled in the art are to be considered as falling within the scope of the present application as defined by the appended claims. The processes, conditions, reagents, experimental methods, etc. described in the following examples are illustrative only and are not intended to limit the scope of the application. The application is not limited to the particular details of the examples.

[0036] Example 1

[0037] This example provides a method for fabricating a surface passivated Sb2Se3 thin film solar cell on a transparent ITO conductive glass substrate, which comprises the following steps:

[0038] 1) ITO conductive glass cleaning: the ITO conductive glass substrate is first cleaned with a solution containing a cleaning agent, then successively washed with acetone and ethanol by ultrasonic washing, finally rinsed with deionized water and dried with high-purity nitrogen blowing for standby.

[0039] 2) deposition of the electron transport layer CdS thin film: a CdS thin film layer is formed on the clean ITO conductive glass substrate by chemical deposition technology. A 20 mg / ml CdCl2 anhydrous ethanol solution is used to maintain 3000 r / s for 30 s, and then short-time annealing at 400°C hot air for 5 min to improve the crystallinity of the thin film, and the CdS thin film thickness is 60 nm.

[0040] 3) growth of the absorption layer Sb2Se3 thin film: Sb2Se3 thin film is deposited on the CdS layer by vapor phase transport technology. The temperature is increased to 520°C at a rate of 20°C / min during the process, maintained at about 3 Pa for 3 min, and then the device is naturally cooled to ambient temperature, and the Sb2Se3 thin film thickness is 1200 nm.

[0041] 4) deposition of the passivation layer P(VDF-TrFE) thin film: before applying the P(VDF-TrFE) passivation layer, the P(VDF-TrFE) material needs to be pretreated:

[0042] a. Dissolve P(VDF-TrFE) in diethyl carbonate at a ratio of 2.5wt%, and heat in a 60°C water bath for 4 hours to speed up the dissolution;

[0043] b. The solution was then uniformly dropped onto the surface of the Sb2Se3 thin film and a passivation layer was formed by spin-coating technique. The initial spin-coating speed was set to 500 r / s for 5 s, and then accelerated to 3000 r / s for 25 s;

[0044] c. After the spin-coating was completed, the sample was baked at 135 °C for 30 min to evaporate the residual solvent, and this process can be repeated to increase the thickness of the passivation layer;

[0045] d. Then, in order to improve the performance stability of the passivation layer, the spin-coated sample was heat-treated at 135 °C for 4 hours, and the thickness of the P(VDF-TrFE) thin film was 30 nm.

[0046] 5) Finally, a gold electrode with a thickness of 100 nm was deposited on the P(VDF-TrFE) thin film passivation layer by thermal evaporation method under vacuum conditions.

[0047] Comparative Example 1

[0048] In this comparative experiment, a standard Sb2Se3 thin film solar cell was prepared without the application of a passivation layer technology. The following steps are the same as Example 1, except for the absence of the passivation layer:

[0049] 1) ITO conductive glass cleaning: consistent with step 1) of Example 1;

[0050] 2) Deposition of electron transport layer CdS thin film: same as step 2) of Example 1;

[0051] 3) Growth of absorber layer Sb2Se3 thin film: same as step 3) of Example 1;

[0052] 4) Deposition of gold electrode layer on Sb2Se3 thin film: same as step 5) of Example 1; i.e. without spin-coating a layer of P(VDF-TrFE) thin film passivation layer on the Sb2Se3 absorber layer, thereby obtaining a Sb2Se3 thin film solar cell without a passivation layer.

[0053] 5) Deposition of gold electrode on P(VDF-TrFE) passivation layer: same as step 5) of Example 1; Sb2Se3 thin film solar cell with P(VDF-TrFE) passivation layer was prepared.

[0054] Reference Figures 2-3 By comparing Example 1 with Comparative Example 1, the XRD results confirm that the addition of 2.5 wt% P(VDF-TrFE) does not result in the generation of new impurities, and the XRD diffraction peaks of the passivated Sb2Se3 thin film with P(VDF-TrFE) are significantly reduced. In addition, Figure 3 a and Figure 3b are SEM images of Sb2Se3 thin film without passivation and with P(VDF-TrFE) passivation, respectively. The P(VDF-TrFE) nanoparticles produced exhibit good dispersibility in diethyl carbonate solvent.

[0055] Further reference is made to Figure 4 The data of Example 1 and Comparative Example 1 confirm that the P(VDF-TrFE) in Example 1 can effectively reduce the defect density on the surface of the absorption layer and adjust the energy band structure at the interface, thereby significantly enhancing the overall performance of the solar cell device.

[0056] The above-described examples demonstrate the preferred implementation of the present application, however, various modifications and changes can be made by those skilled in the art in light of the above teachings without departing from the spirit and scope of the present application. Such changes can include substitution and adjustment of materials, dimensions, or process parameters, and such adjustments, as long as they do not deviate from the spirit and essence of the present application, should be considered as equivalent implementations within the scope of protection of the present application.

Claims

1. A passivated antimony selenide thin-film solar cell, characterized in that, The battery consists of, from bottom to top: an indium tin oxide transparent conductive glass front electrode substrate, an electron transport layer, an absorption layer, a passivation layer, and a back electrode layer. The electron transport layer is a cadmium sulfide thin film with a thickness of 20–150 nm; The absorption layer is an antimony selenide thin film with a thickness of 200–2000 nm; The passivation layer is a polyvinylidene fluoride-trifluoroethylene copolymer film with a thickness of 10-150 nm; The back electrode layer is a gold electrode thin film with a thickness of 50–150 nm; The preparation of the passivated antimony selenide thin-film solar cell includes the following steps: 1) Cleaning of the front electrode substrate of indium tin oxide transparent conductive glass: First, clean with a solution containing detergent, then perform continuous ultrasonic cleaning with acetone and ethanol, and finally rinse with deionized water and purge with high-purity nitrogen until dry for later use. 2) Preparation of cadmium sulfide thin film for electron transport layer: Cadmium sulfide thin film was deposited on the substrate in step 1) by chemical water bath method. The cadmium sulfide thin film was spin-coated with 20 mg / ml CdCl2 ethanol solution at a spin speed of 2000 r / s for 30 s. Then, it was annealed at 350-450℃ for 5 min to form electron transport layer with a thickness controlled between 20 and 150 nm. 3) Preparation of the antimony selenide thin film as the absorption layer: Antimony selenide thin film was deposited on cadmium sulfide thin film using a gas phase transport method. During the process, the heating rate was controlled at 20-100℃ / min, the temperature was raised to 450-550℃, held at 2.5-3.5 Pa for 2-5 min, and then naturally cooled to room temperature. The resulting antimony selenide thin film served as the absorption layer with a thickness of 200-2000 nm. 4) Preparation of the passivation layer polyvinylidene fluoride-trifluoroethylene copolymer film: First, prepare a copolymer solution of 2-10 wt%, using diethyl carbonate as the solvent; spin-coat the solution onto the surface of the antimony selenide film, first maintaining a spin speed of 300-1000 r / s for 5-10 s, then maintaining a spin speed of 2000-4000 r / s for 10-25 s; during the drying process, first place it in an environment of 90-120℃ for 10-60 min to promote solvent evaporation, then maintain it in an environment of 135-165℃ for 2-8 hours to improve the crystallinity of the film, forming a polyvinylidene fluoride-trifluoroethylene copolymer film with a thickness of 10-150 nm, i.e., the passivation layer; 5) Preparation of the gold electrode thin film for the back electrode layer: Under vacuum conditions, a gold electrode layer is deposited on the polyvinylidene fluoride-trifluoroethylene copolymer film by thermal evaporation, with the thickness controlled at 50-150 nm, to complete the preparation of the passivated antimony selenide thin film solar cell.

2. The antimony selenide thin-film solar cell according to claim 1, characterized in that, Step 4) The passivation layer polyvinylidene fluoride-trifluoroethylene copolymer film can also be prepared according to the following steps: a) Dissolve the polyvinylidene fluoride-trifluoroethylene copolymer in diethyl carbonate at a ratio of 2-10 wt%, and heat it in a water bath at 60°C for 4 hours to accelerate the dissolution of the solute; b) The obtained solution is dropped onto the surface of the antimony selenide film and a film is formed by spin coating. The spin coating process includes two stages: first, spin coating at a speed of 300 to 1000 r / s for 6 to 8 s, and then increasing to 2000 to 4000 r / s and maintaining for 15 to 20 s. c) Place the sample coated with the polyvinylidene fluoride-trifluoroethylene copolymer film in an environment of 100-110°C for 20-40 min to promote solvent evaporation; then, under the same conditions, spin-coat a second layer of polyvinylidene fluoride-trifluoroethylene copolymer solution; repeat this process several times to obtain a polyvinylidene fluoride-trifluoroethylene copolymer film of the desired thickness, which is 10-150 nm. d) Place the sample coated with the polyvinylidene fluoride-trifluoroethylene copolymer film in an environment of 140-160°C for 3-7 hours to complete the preparation of the passivation layer.

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