Method for inhibiting oxidation-reduction reaction of nickel oxide / perovskite interface in perovskite solar cell

Abstract

The invention relates to a method for inhibiting oxidation-reduction reaction of a nickel oxide / perovskite interface in a perovskite solar cell. The method comprises the following specific steps: S1, firstly, preparing a compact base nickel oxide film on a conductive substrate; s2, heating an acetone solvent to obtain acetone steam, and performing reductive treatment on the substrate nickel oxide film to achieve the purpose of passivating high-valence nickel ions on the surface of nickel oxide; and S3, continuing to deposit a perovskite precursor on the nickel oxide thin film subjected to acetone steam treatment, and performing heating annealing treatment to obtain a high-quality perovskite thin film. Through the method, surface defects of the nickel oxide thin film can be passivated, the energy level structure of the nickel oxide thin film can be regulated and controlled, the stability of the perovskite thin film is improved, and the photoelectric property of a solar cell based on the thin film is also remarkably improved. The method is simple and convenient to operate, low in raw material price and suitable for industrial large-scale production.

Description

Technical Field

[0001] The invention belongs to the field of perovskite films, and specifically relates to a method for inhibiting the redox reaction of a nickel oxide / perovskite interface in a perovskite solar cell. The method is a method for reducing high-valent nickel ion defects on the surface of nickel oxide and inhibiting the redox reaction of the nickel oxide / perovskite interface. Specifically, the purpose of passivating the high-valent nickel ions on the surface of the nickel oxide is achieved by subjecting the surface of the nickel oxide film to a reducing treatment with acetone vapor at a certain temperature, thereby inhibiting the redox reaction of the nickel oxide / perovskite interface and reducing the decomposition rate of the perovskite film to improve the stability of the perovskite film and the photoelectric performance of the perovskite solar device. Background Art

[0002] Inverse perovskite solar cells are conducive to commercial applications due to their reliable operating stability, negligible hysteresis effect and low-temperature preparation process. In addition to the role of carrier extraction and transport, the hole transport layer in inverse perovskite solar cells also plays a very important role in the crystallization and growth of the perovskite layer as the substrate of the perovskite layer. x Relying on its superior chemical stability and low material cost, it has a good development prospect. However, based on NiO x The highest efficiency of inverse perovskite solar cells with hole transport layers is still lower than the photoelectric efficiency of organic hole transport layers, and NiO x The high surface defects, low intrinsic conductivity and energy level mismatch of the hole transport layer with the perovskite layer are the reasons for the low efficiency and poor stability of perovskite solar cells. x It is a semiconductor material with intrinsic cation vacancies. During the preparation process, part of the Ni 2+ ions will be converted into Ni≥3+ ions. However, NiO x The high-valence Ni≥3+ ions on the film surface act as Proton acceptors and Lewis electron acceptors can easily undergo redox reactions with organic methylamine and formamidine cations in perovskite, thereby decomposing the perovskite to form a thinner lead iodide hole extraction barrier, resulting in a decrease in battery efficiency and stability.

[0003] Currently commonly used passivation NiO x The surface defect method mainly uses organic materials such as poly [bis (4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) and [2- (3,6-dimethoxy-9H-carbazole-9-yl) ethyl] phosphonic acid (MeO-2PACz). Although the passivation effect is good, these organic materials are relatively expensive and the stability improvement is not obvious, which is not conducive to the application in the production of large-area commercial perovskite solar cells.

[0004] Therefore, finding a low-cost and easy-to-operate method to perform reductive treatment on the surface of nickel oxide film to passivate surface defects and change the energy level structure of nickel oxide film is of great significance to comprehensively improve the stability and photoelectric performance of perovskite solar cells. Summary of the invention

[0005] In view of the defects of the prior art, the present invention relates to a method for inhibiting the redox reaction at the interface of nickel oxide / perovskite in a perovskite film, which can improve the stability of perovskite solar devices, specifically a method for improving the ability of nickel oxide to extract hole carriers by passivating the surface defects of nickel oxide and regulating the energy level structure. The commonly used redox methods are mainly concentrated in solution methods, such as urea solution and nitric acid solution, but the solution method is difficult to apply in large-area perovskite solar cell module devices, mainly because the solution method has a large area substrate (5×5cm 2 The above) will cause uneven coverage, and the use of the reductive steam rule can perfectly solve the problem of uneven coverage in the preparation process of large-area devices. Reducing the content of high-valent nickel ions on the surface of the nickel oxide film by acetone vapor can inhibit the redox reaction at the nickel oxide / perovskite interface and reduce the rate of perovskite decomposition. At the same time, acetone vapor treatment can regulate the energy level structure of the nickel oxide film, increase the work function of the nickel oxide film and reduce the position of the valence band energy level, promote better energy level matching with the perovskite layer, improve the ability of hole extraction and transmission, and ultimately improve the stability of the perovskite film and the photoelectric performance of the device.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for inhibiting the redox reaction at the nickel oxide / perovskite interface in a perovskite solar cell, the method comprising the following steps:

[0008] S1. preparing a dense base nickel oxide film on a conductive substrate;

[0009] S2, placing the substrate nickel oxide film in acetone vapor to perform a reducing treatment on it;

[0010] S3. Depositing a perovskite precursor on the nickel oxide film after the reduction treatment, and heating and annealing the film to obtain a perovskite film.

[0011] Preferably, in step S1, the conductive substrate comprises one of an ITO and a FTO conductive substrate.

[0012] Preferably, in step S1, the nickel oxide film includes one of a nanocrystalline nickel oxide film, a magnetron nickel oxide film, a sol-gel nickel oxide film, a sprayed nickel oxide film, and an atomic layer deposition nickel oxide film.

[0013] Preferably, in step S2, the acetone vapor is obtained by heating the acetone solvent to promote the volatilization of the acetone vapor; the acetone selected in the present invention has a very low volatilization temperature, is easy to operate at low temperature, is inexpensive, and reacts mildly with nickel oxide, and is easy to improve the uniformity of the reaction. The heating temperature is 40-100°C, preferably 40-60°C. The time of the reduction treatment is 15-30min. The acetone vapor obtained by heating the acetone solvent is subjected to a reduction treatment on the base nickel oxide film to achieve the purpose of passivating the high-valent nickel ions on the surface of the nickel oxide. The passivation treatment refers to passivating the surface defects of the nickel oxide by acetone vapor and promoting the matching of the nickel oxide / perovskite interface energy levels.

[0014] Preferably, in step S3, the obtained perovskite film is an organic-inorganic hybrid lead halide perovskite film ABX3, wherein A includes one or more of FA, MA, and Cs; B is Pb; and X includes one of I, Br, and Cl.

[0015] Preferably, in step S3, the temperature of the heating annealing treatment is 100-120° C., and the time is 10-30 min, preferably annealing at 100° C. for 30 min.

[0016] The present invention uses acetone vapor, which is easy to operate, to passivate the surface defects of the nickel oxide hole transport layer and regulate the energy level structure of the nickel oxide film, ultimately achieving the dual purpose of improving the stability of the perovskite film and the photoelectric performance of the corresponding device.

[0017] The present invention also provides a perovskite solar cell device, and a complete perovskite solar cell device is obtained by sequentially preparing PCBM, BCP and Ag electrode on the perovskite film.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention uses acetone vapor to passivate the surface defects of the nickel oxide film. The raw materials are cheap, the operation is simple and feasible, and it is easy to carry out large-scale industrial production.

[0020] (2) The present invention aims to inhibit harmful redox reactions at the buried interface of perovskite solar cells, thereby achieving an overall improvement in the performance and stability of perovskite solar cells;

[0021] (3) The nickel oxide films deposited by physical vapor deposition and solution method treated by the method of the present invention have good passivation effects and can effectively improve the photoelectric conversion efficiency of perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0023] Figure 1 NiO in Comparative Example 1 of the present invention x X-ray diffraction pattern of the film;

[0024] Figure 2 NiO in Comparative Example 1 x Optical transmittance graph of the film;

[0025] Figure 3 NiO in Comparative Example 1 x X-ray photoelectron spectroscopy of thin films;

[0026] Figure 4 NiO in Comparative Example 1 x UV photoelectron spectrum of the film;

[0027] Figure 5 is the photoluminescence image of the perovskite film in Comparative Example 1;

[0028] Figure 6 is a JV curve diagram of the device obtained in Comparative Example 1;

[0029] Figure 7 NiO in Example 1 of the present invention x X-ray diffraction pattern of the film;

[0030] Figure 8 NiO in Example 1 x Optical transmittance graph of the film;

[0031] Fig. 9 NiO in Example 1 x X-ray photoelectron spectroscopy of thin films;

[0032] Fig.10 NiO in Example 1 x UV photoelectron spectrum of the film;

[0033] Fig.11 is a photoluminescence image of the perovskite film in Example 1;

[0034] Fig.12 is a JV curve diagram of the device obtained in Example 1;

[0035] Fig.13 This is a structural diagram of the perovskite solar cell device in the present invention. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0037] The present invention provides a method for inhibiting nickel oxide / perovskite interface redox reaction and improving the stability of perovskite solar device, the method comprising the following steps:

[0038] S1. First, a dense base nickel oxide film is prepared on an ITO conductive substrate;

[0039] S2, heating the acetone solvent to obtain acetone vapor to perform a reducing treatment on the nickel oxide film on the substrate to passivate the high-valent nickel ions on the surface of the nickel oxide;

[0040] S3. Continue to deposit the perovskite precursor on the nickel oxide film treated with acetone vapor and heat and anneal to obtain a high-quality perovskite film.

[0041] In step S1, the nickel oxide film is a nanocrystalline nickel oxide film, a magnetron nickel oxide film, a sol-gel nickel oxide film, a sprayed nickel oxide film and an atomic layer deposition nickel oxide film.

[0042] In step S2, the acetone vapor is obtained by heating the acetone solvent to a specified temperature to promote the volatilization of the acetone vapor.

[0043] In step S2, the passivation treatment refers to passivating the surface defects of nickel oxide and promoting the energy level matching of nickel oxide / perovskite interface by acetone vapor.

[0044] In step S3, the perovskite film is an ABX3 (A=FA, MA, Cs; B=Pb; X=I, Br, Cl) organic-inorganic hybrid lead halide perovskite film.

[0045] Comparative Example 1

[0046] This comparative example mainly relates to an inverted perovskite solar cell device based on a NiOx hole transport layer that has not been treated in any way, and the method comprises the following steps:

[0047] (1) Preparation of dense NiO with a thickness of about 20 nm on an ITO conductive substrate x Hole transport layer: The hole transport layer in this comparative example is a nanocrystalline nickel oxide film, and the preparation method is as follows: first, 30 mg / mL of nickel oxide nanocrystalline powder is uniformly dispersed in deionized water, and a nickel oxide film is obtained by spin coating on a conductive substrate, and finally, a dense and uniform nickel oxide hole transport layer is obtained by annealing at 120° C. for 10 minutes;

[0048] (2) Take 50uL Cs 0.05 FA 0.95 PbI3 perovskite precursor is evenly dispersed in NiO x The substrate was prepared by spin coating, and a high-quality perovskite film of about 500 nm was obtained by chlorobenzene anti-solvent extraction and annealing at 100 °C for 30 min;

[0049] (3) PCBM, BCP and Ag electrodes are prepared on the perovskite film in sequence to obtain a complete perovskite solar cell device.

[0050] Example 1

[0051] Compared with Comparative Example 1, this embodiment mainly adds a step of treating the nickel oxide film with acetone vapor. The method includes the following steps:

[0052] (1) Preparation of dense NiO with a thickness of about 20 nm on an ITO conductive substrate x hole transport layer;

[0053] (2) By mixing acetone solvent and NiO x The film was placed in a closed culture dish and heated to 40°C for 20 min to obtain Acetone-NiO x Hole transport layer.

[0054] (3) Take 50uL Cs 0.05 FA 0.95 PbI3 perovskite precursor is evenly dispersed in NiO x The substrate was prepared by spin coating, and a high-quality perovskite film of about 500 nm was obtained by chlorobenzene anti-solvent extraction and annealing at 100 °C for 30 min;

[0055] (4) PCBM, BCP and Ag electrodes are sequentially prepared on the perovskite film to obtain a complete perovskite solar cell device with the structure as shown in FIG. Fig.13 shown.

[0056] Figure 1 and Figure 2 This shows that in the comparative example we obtained NiO with higher crystalline quality. x The hole transport layer, while maintaining a high optical transmittance, allows more visible light to be absorbed by the perovskite layer to increase the short-circuit current of the perovskite solar device. Figure 7 and Figure 8 It shows that after acetone vapor treatment in Example 1, NiO x The crystal quality and optical transmittance of the hole transport layer did not change significantly and were well maintained. Figure 3 Comparative Example NiO xThe XPS spectrum of Ni element in the film can be analyzed to obtain Ni 3+ / Ni 2+ The content ratio is 2.99, and Fig. 9 Acetone vapor treated NiO of Example 1 x Thin film Ni 3+ / Ni 2+ The content ratio of NiO decreased to 2.27, which means that x The high-valent nickel ions on the film surface are reduced by acetone vapor, thereby passivating surface defects and inhibiting the redox reaction at the nickel oxide / perovskite interface. Figure 4 and Fig.10 NiO x The UPS spectrum of the film can be used to calculate the comparative NiO x The work function and valence band energy level of the film are 4.71 and -5.26 eV respectively. x The work function of the film can be increased to 4.76eV, and the valence band energy level also moves to a deeper -5.33eV. The change in the energy level structure can make NiO x The hole transport layer and the perovskite layer are more energy-level matched, which improves the extraction and transport capabilities of hole carriers. x Surface defect passivation and energy level structure regulation of thin films, Figure 5 and Fig.11 Compared with the PL luminescence intensity of the perovskite film of Comparative Example 1, the PL luminescence intensity of the perovskite film of Example 1 is significantly reduced, which indicates that the acetone vapor treatment of NiO x The hole transport layer has better hole extraction capability. Figure 6 The open circuit voltage of the perovskite solar cell device based on Comparative Example 1 is 1.03 V and the short circuit current density is 25.0 mA / cm 2 , the filling factor is 0.778 and the photoelectric conversion efficiency is 20.07%. Thanks to the lower surface defects and more matching energy level structure of the NiOx hole transport layer treated with acetone vapor, such as Fig.12 The open circuit voltage and fill factor of the perovskite solar cell based on Example 1 are significantly improved, the open circuit voltage is increased to 1.09V, and the short circuit current density is 24.8mA / cm 2 , the filling factor increased to 0.825, and the final photoelectric conversion efficiency increased to 22.30%.

[0057] Example 2

[0058] The difference between this embodiment and embodiment 1 is that NiO xThe hole transport layer is different, it is a magnetron nickel oxide film, and the preparation method is as follows: first, a high-purity nickel oxide target is sputtered at a power of 200 W by a magnetron sputtering system in a high vacuum environment, and the volume ratio of Ar / O2 is 100:1. The prepared nickel oxide film is annealed at 200°C in a Malvern furnace for 1 hour to obtain a dense and uniform nickel oxide hole transport layer.

[0059] Comparative Example 2

[0060] This comparative example is basically the same as Example 1, except that: there is no step of treating the nickel oxide film with acetone vapor, but an interface modification layer is prepared on the hole transport layer, and the specific steps are: first, a dense nickel oxide film is prepared by electron beam evaporation, and then the surface wettability of the nickel oxide film is improved by argon plasma treatment, and then a dilute nitric acid solution is dropped on the surface of the nickel oxide film to prepare the interface modification layer by spin coating. Although this method can improve the performance of the overall perovskite solar cell, it is difficult to prepare uniformly in a large-area substrate by the solution method. In comparison, the use of acetone, a reducing vapor, can better reflect the priority of uniform preparation in the process of preparing a large-area substrate. At the same time, the reaction between the steam method and the nickel oxide film will be more gentle, which can also reflect the priority of uniform reaction.

[0061] The present invention has many specific application paths, and the above is only a preferred embodiment of the present invention. It should be pointed out that the above embodiments are only used to illustrate the present invention, and are not used to limit the protection scope of the present invention. For those of ordinary skill in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A method for inhibiting redox reactions at the nickel oxide / perovskite interface in a perovskite solar cell, characterized in that: The method comprises the following steps: S1. preparing a dense base nickel oxide film on a conductive substrate; S2, placing the substrate nickel oxide film in acetone vapor to perform a reducing treatment on it; S3. Depositing a perovskite precursor on the reductively treated nickel oxide film, and performing heating and annealing treatment to obtain a perovskite film.

2. The method according to claim 1, characterized in that In step S1, the conductive substrate includes one of an ITO and a FTO conductive substrate.

3. The method according to claim 1, characterized in that In step S1, the nickel oxide film includes one of a nanocrystalline nickel oxide film, a magnetron nickel oxide film, a sol-gel nickel oxide film, a sprayed nickel oxide film, and an atomic layer deposition nickel oxide film.

4. The method according to claim 1, characterized in that In step S2, the reducing treatment time is 15-30 minutes.

5. The method according to claim 1, characterized in that In step S2, the acetone vapor is obtained by heating the acetone solvent to promote the volatilization of the acetone vapor; the heating temperature is 40-100°C.

6. The method according to claim 1, characterized in that In step S3, the obtained perovskite film is an organic-inorganic hybrid lead halide perovskite film ABX3, wherein A includes one or more of FA, MA, and Cs; B is Pb; and X includes one of I, Br, and Cl.

7. The method according to claim 1, characterized in that In step S3, the temperature of the heating annealing treatment is 100° C. and the time is 30 minutes.

8. A perovskite solar cell device, characterized in that: The perovskite solar cell device is obtained by sequentially preparing PCBM, BCP and Ag electrodes on the perovskite film obtained by the method according to claim 1.

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