A method for improving the efficiency and stability of perovskite solar cells

Abstract

The present invention provides a method for improving the efficiency and stability of perovskite solar cells, which relates to the technical field of perovskite solar cells. The method for improving the efficiency and stability of perovskite solar cells includes the following specific contents: S1. Using a metal Ti sheet substrate as the anode and a Pt wire as the cathode, a series of TiO2 nanotube structures are prepared by selecting appropriate electrochemical anodization parameters, and annealed at 450 °C to transform the amorphous nanotubes into anatase crystal form; S2. The surface of the TiO2 nanostructure is doped with metal sodium ions by controlling the reverse voltage to regulate the surface states and interfacial crystal structures of the TiO2 nanostructure. By doping the surface of the TiO2 nanostructure with cations, it is expected to eliminate the surface impurities of the TiO2 nanostructure, reduce the electron-hole recombination generated at the TiO2 / perovskite interface in the perovskite solar cell, and improve the efficiency and stability of the perovskite solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and particularly to a method for improving the efficiency and stability of perovskite solar cells. Background Art

[0002] In recent years, lead halide perovskite (CH3NH3PbX3, X = Cl, Br, I) has been regarded as a star material for a new generation of photovoltaic cells due to its characteristics such as a wide absorption spectrum, a high extinction coefficient, and a high carrier mobility. In just a few years, researchers have increased the efficiency of perovskite (CH3NH3PbI3) solar cells from 3.8% to over 20% through methods such as using solid-state electrolytes, optimizing the electron transport layer structure, and improving the cell structure, and there is further room for development. Although perovskite photovoltaic cells have achieved exciting experimental results in recent years, high efficiency and high stability are key factors for achieving final industrialization. It has been reported that the efficiency of a thin-film solar cell based on CH3NH3PbI3 decreased from 19.3% to 5% within 6 days.

[0003] In recent years, perovskite solar cells have become a research hotspot worldwide due to their ultra-high efficiency, but poor stability has become a bottleneck for their application. Among the many factors affecting cell performance, the TiO2 / perovskite interface plays a decisive role. First, due to the large specific surface area of nanomaterials (TiO2), surface atoms are mismatched and it is easy to form unsaturated bonds (such as Ti 3+ etc.), resulting in surface defects or surface dangling bonds, and generating electron-hole recombination at the interface; second, due to reasons such as the low electron mobility and poor conductivity of traditional TiO2 nanoparticles, the transport speed and efficiency of photo-generated electrons are low, which in turn affects the yield of photo-generated electrons and holes transferred from the TiO2 / perovskite interface to the electrode, reducing the photocurrent of perovskite solar cells; in addition, the energy level structure of the TiO2 / perovskite interface directly determines the transport and separation of charges, affecting the efficiency and stability of the cell.

[0004] Therefore, we have developed a new method for improving the efficiency and stability of perovskite solar cells. This project proposes to directly prepare a TiO2 nanotube array structure on a metal titanium sheet by electrochemical anodic oxidation to replace the two-layer structure of the dense TiO2 layer (hole blocking layer) and porous nano-TiO2 (electron transport layer) in traditional perovskite solar cells, and to control the reverse voltage to perform surface metal cation (such as Na +)Dope, and measure the surface states and crystal structure of the doped TiO2 by means of synchrotron radiation near-edge fine structure absorption spectroscopy and grazing incidence X-ray diffraction to guide and optimize the doping conditions, eliminate the surface impurity states of the TiO2 nanostructure, and reduce the interfacial electron-hole recombination at the interface between the TiO2 nanostructure and the perovskite. Combine first-principles calculations and photoelectron spectroscopy analysis to regulate the doping amount and optimize the energy level structures of TiO2 and the perovskite to make it more conducive to charge transport, and significantly improve the efficiency and stability of perovskite solar cells. Summary of the Invention

[0005] (1) Technical problems to be solved

[0006] Aiming at the deficiencies of the prior art, the present invention provides a method for improving the efficiency and stability of perovskite solar cells. By cation-regulated doping of TiO2 nanostructures, the problems caused by the surface atom mismatch of traditional TiO2 nanoparticles, resulting in the formation of unsaturated bonds (such as Ti 3+ etc.) and surface defects are solved. Secondly, the present invention directly grows TiO2 nanotubes on a metal Ti sheet, solving the problem of low electron mobility and poor conductivity of traditional TiO2 nanoparticles, resulting in low transfer speed and efficiency of photo-generated electrons in perovskite solar cells. In addition, the invention measures the surface states and crystal structure of doped TiO2 by means of synchrotron radiation spectroscopy and other methods to optimize the doping conditions, and solves the problem of electron-hole recombination caused by interfacial energy level mismatch and other reasons.

[0007] (2) Technical solutions

[0008] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for improving the efficiency and stability of perovskite solar cells, including the following specific contents:

[0009] S1. Use a metal Ti sheet substrate as the anode and a Pt wire as the cathode, and prepare a series of TiO2 nanotube structures by selecting appropriate electrochemical anodization parameters, and perform annealing treatment at 450 °C to transform the amorphous nanotubes into anatase crystal form;

[0010] S2. Control the reverse voltage to dope the surface of the TiO2 nanostructure with metal sodium ions (Na + ) to achieve the regulation of the surface states and interfacial crystal structure of the TiO2 nanostructure;

[0011] S3. Measure the surface state structure of the doped TiO2 by means of synchrotron radiation near-edge fine structure absorption spectroscopy (XANES) to guide and optimize the doping conditions and eliminate the surface impurity states of the TiO2 nanostructure;

[0012] S4. Calculate the influence of the doping amount on the energy levels of TiO2 based on first principles, and obtain a matching energy level structure of the TiO2 / perovskite CH3NH3PbI3 interface;

[0013] S5. Based on synchrotron radiation grazing incidence X-ray diffraction to measure the crystal structure of the TiO2 / perovskite CH3NH3PbI3 interface, combined with near-edge fine absorption structure spectroscopy and first-principles calculations, improve the doping conditions to further optimize the energy levels at the interface, and obtain a stable and efficient perovskite solar cell device.

[0014] Preferably, in step S2, an appropriate positive voltage is applied to the surface for surface activation to remove surface debris before doping. Since the surface of the TiO2 nanostructure prepared by the electrochemical anodization method is often blocked by grass-like deposits, doping is difficult to effectively carry out. Therefore, an appropriate positive voltage needs to be applied to the surface for surface activation to remove surface debris before doping to achieve effective cation doping. By adjusting the doping amount of cations, the unsaturated bonds and impurity states of the TiO2 nanostructure are eliminated, thereby reducing the electron-hole recombination at the TiO2 / CH3NH3PbI3 interface. At the same time, this method has universality for the surface property regulation of nanomaterials.

[0015] Preferably, in step S3, the surface state structure of the doped TiO2, including unsaturated bonds and impurity states, is measured by synchrotron radiation near-edge fine structure absorption spectroscopy (XANES). By studying the changes in the local structure (unsaturated bonds, impurity states, etc.) on the surface of TiO2 in real time, the doping conditions can be further optimized to eliminate surface impurity states. By studying the influence law of the energy level structure of the TiO2 / CH3NH3PbI3 interface on the performance of perovskite solar cells, the doping conditions are optimized to regulate the energy levels and local structure at the interface, so that the efficiency of the battery reaches more than 15%, and the attenuation within 2 hours is controlled within 3%.

[0016] Preferably, in step S5, based on synchrotron radiation grazing incidence X-ray diffraction analysis, the incident angle between the incident X-ray and the sample can be accurately changed, and then the appropriate interface analysis depth can be reached, enabling the crystal structure analysis of the TiO2 / CH3NH3PbI3 interface. Since the TiO2 / CH3NH3PbI3 interface is buried under the surface, regulating the analysis depth of grazing incidence X-ray diffraction is the key. The grazing incidence X-ray diffraction test based on synchrotron radiation can accurately control the rotation stage of the sample to achieve an angular control of 0.01 degrees, and then reach the appropriate interface analysis depth.

[0017] (III) Beneficial effects

[0018] The present invention provides a method for improving the efficiency and stability of perovskite solar cells. It has the following beneficial effects:

[0019] 1. The method for improving the efficiency and stability of perovskite solar cells eliminates surface impurities of the TiO2 nanostructure by surface cation doping of the TiO2 nanostructure, reduces electron-hole recombination generated at the TiO2 / CH3NH3PbI3 perovskite interface in the perovskite solar cell, and improves the efficiency and stability of the perovskite solar cell.

[0020] 2. The method for improving the efficiency and stability of perovskite solar cells changes its energy level structure by regulating the TiO2 doping amount, making the energy levels at the TiO2 / CH3NH3PbI3 perovskite interface conducive to charge transport, and improving the efficiency of the perovskite solar cell.

[0021] 3. The method for improving the efficiency and stability of perovskite solar cells establishes the connection between the energy level structure and photovoltaic performance at the TiO2 / CH3NH3PbI3 perovskite interface through a new method combining synchrotron radiation spectroscopy analysis and first-principles calculation. Description of the Drawings

[0022] Figure 1 It is the scanning electron microscope image of the TiO2 nanotubes after annealing of the present invention;

[0023] Figure 2 It is the schematic diagram of the perovskite film formation structure on the surface of TiO2 in the state of no cation doping of the present invention;

[0024] Figure 3 It is the perovskite film formation structure diagram on the surface of TiO2 in the state of light cation doping of the present invention;

[0025] Figure 4 It is the perovskite film formation structure diagram on the surface of TiO2 in the state of heavy cation doping of the present invention;

[0026] Figure 5 It is the synchrotron radiation near-edge fine absorption structure diagram of undoped TiO2 and Na-doped TiO2 nanotubes of the present invention;

[0027] Figure 6 It is the crystal structure diagram of the undoped TiO2 / perovskite CH3NH3PbI3 interface measured by synchrotron radiation grazing incidence X-ray diffraction of the present invention;

[0028] Figure 7 It is the crystal structure diagram of the lightly doped TiO2 / perovskite CH3NH3PbI3 interface measured by synchrotron radiation grazing incidence X-ray diffraction of the present invention;

[0029] Figure 8 It is the crystal structure diagram of the heavily doped TiO2 / perovskite CH3NH3PbI3 interface measured by synchrotron radiation grazing incidence X-ray diffraction of the present invention. Detailed Embodiments

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0031] Embodiment:

[0032] As Figure 1-8 shown, the embodiments of the present invention provide a method for improving the efficiency and stability of perovskite solar cells, including the following specific contents:

[0033] S1. Using a metal Ti sheet substrate as the anode and a Pt wire as the cathode, a series of TiO2 nanotube structures are prepared by selecting appropriate electrochemical anodization parameters, and annealed at 450 °C to transform the amorphous nanotubes into anatase crystal form;

[0034] S2. By controlling the reverse voltage, the surface of the TiO2 nanostructure is doped with metal sodium ions (Na + ), to realize the regulation of the surface states and interface crystal structures of the TiO2 nanostructure;

[0035] S3. Measuring the surface state structure of the doped TiO2 by means of synchrotron radiation near-edge fine structure absorption spectroscopy (XANES) to guide and optimize the doping conditions and eliminate the surface impurity states of the TiO2 nanostructure;

[0036] S4. According to the first-principles, calculate the influence of the doping amount on the energy levels of TiO2 to obtain a matching TiO2 / perovskite CH3NH3PbI3 interface energy level structure;

[0037] S5. Based on synchrotron radiation grazing incidence X-ray diffraction to measure the crystal structure of the TiO2 / perovskite CH3NH3PbI3 interface, combined with the near-edge fine absorption structure spectrum and the first-principles calculation, improve the doping conditions to further optimize the interface energy levels and obtain a stable and efficient perovskite solar cell device.

[0038] In S2, an appropriate positive voltage is applied before doping for surface activation to remove surface debris. Since the surface of the TiO2 nanostructure prepared by the electrochemical anodic oxidation method is often blocked by grass-like deposits, doping is difficult to carry out effectively. Therefore, an appropriate positive voltage needs to be applied before doping for surface activation to remove surface debris, realizing effective cation doping. By adjusting the doping amount of cations, the unsaturated bonds and impurity states of the TiO2 nanostructure are eliminated, thereby reducing the electron-hole recombination at the TiO2 / CH3NH3PbI3 interface. At the same time, this method has universality for the surface property regulation of nanomaterials.

[0039] In S3, the surface state structure of doped TiO2, including unsaturated bonds and impurity states, is measured by synchrotron radiation near-edge fine structure absorption spectroscopy (XANES). By studying the changes in the local structure (unsaturated bonds, impurity states, etc.) on the TiO2 surface in real time, the doping conditions can be further optimized to eliminate surface impurity states. By studying the influence law of the energy level structure of the TiO2 / CH3NH3PbI3 interface on the performance of perovskite solar cells, the doping conditions are optimized to regulate the interface energy level and local structure, making the efficiency of the battery reach more than 15% and the attenuation within 3% in 2 hours.

[0040] In S5, based on synchrotron radiation grazing incidence X-ray diffraction analysis, the incident angle between the incident X-ray and the sample can be precisely changed, and then an appropriate interface analysis depth can be reached, enabling the crystal structure analysis of the TiO2 / CH3NH3PbI3 interface. Since the TiO2 / CH3NH3PbI3 interface is buried under the surface, regulating the incident angle of grazing incidence X-ray diffraction is the key to the analysis depth. The grazing incidence X-ray diffraction test based on synchrotron radiation can precisely control the rotation stage of the sample to achieve an angular control of 0.01 degrees, and then reach the appropriate interface analysis depth.

[0041] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving the efficiency and stability of perovskite solar cells, characterized in that: It includes the following specific contents: S1. Using a metal Ti sheet substrate as the anode and a Pt wire as the cathode, a series of TiO2 nanotube structures are prepared by selecting appropriate electrochemical anodization parameters, and annealed at 450 °C to transform the amorphous nanotubes into anatase crystal form; S2. The surface metal sodium ions of the TiO2 nanostructure are doped by controlling the reverse voltage to regulate the surface states and interfacial crystal structure of the TiO2 nanostructure; S3. Measuring the surface state structure of the doped TiO2 with the help of synchrotron radiation near-edge fine structure absorption spectroscopy to guide and optimize the doping conditions and eliminate the surface impurity states of the TiO2 nanostructure; S4. According to the first principles, calculate the influence of the doping amount on the energy level of TiO2 to obtain a matching TiO2 / perovskite CH3NH3PbI3 interfacial energy level structure; S5. Based on synchrotron radiation grazing incidence X-ray diffraction to measure the crystal structure of the TiO2 / perovskite CH3NH3PbI3 interface, combined with the near-edge fine absorption structure spectrum and first principles calculation, improve the doping conditions to further optimize the interfacial energy level and obtain a stable and efficient perovskite solar cell device.

2. A method for improving the efficiency and stability of a perovskite solar cell according to claim 1, characterized in that: In S2, an appropriate positive voltage is applied to it for surface activation to remove surface debris before doping.

3. A method for improving the efficiency and stability of a perovskite solar cell according to claim 1, characterized in that: In S3, measuring the surface state structure of the doped TiO2 with the help of synchrotron radiation near-edge fine structure absorption spectroscopy includes unsaturated bonds and impurity states.

4. A method for improving the efficiency and stability of a perovskite solar cell according to claim 1, characterized in that: In S5, based on synchrotron radiation grazing incidence X-ray diffraction analysis, the incident angle between the incident X-ray and the sample can be accurately changed, and then the appropriate interface analysis depth can be reached.

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