A method for inhibiting the oxidation-reduction reaction of the nickel oxide / perovskite interface in a perovskite solar cell

Abstract

The present application relates to a kind of methods for inhibiting perovskite solar cell nickel oxide / perovskite interface redox reaction.The method of the present application, specific steps are as follows: S1, first prepare dense substrate nickel oxide film on conductive substrate;S2, acetone solvent heating obtains acetone vapor to substrate nickel oxide film does reduction treatment to achieve the purpose of passivating high valence nickel ion on nickel oxide surface;S3, continue to deposit perovskite precursor on the nickel oxide film treated by acetone vapor and heat annealing treatment to obtain high-quality perovskite film.By this method, the surface defects of nickel oxide film can be passivated, the energy level structure of nickel oxide film can be regulated, the stability of perovskite film can be improved, and the photoelectric performance of solar cell based on the film is also significantly improved.The method is simple and convenient to operate, the raw material price is low, and it is suitable for industrial large-scale production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of perovskite thin films, and particularly relates to a method for inhibiting the oxidation-reduction reaction at the interface between nickel oxide and perovskite in a perovskite solar cell. Specifically, the method is to pass acetone vapor at a certain temperature to reduce the surface of the nickel oxide film, so as to passivate the high-valence nickel ions on the surface of the nickel oxide, thereby inhibiting the oxidation-reduction reaction at the interface between nickel oxide and perovskite, and reducing the decomposition rate of the perovskite thin film to improve the stability of the perovskite thin film and the photoelectric performance of the perovskite solar device. BACKGROUND

[0002] The trans perovskite solar cell is conducive to commercial application due to its reliable operation stability, negligible hysteresis effect and low-temperature preparation process. In the trans perovskite solar cell, the hole transport layer not only plays a role in carrier extraction and transport, but also has a very important influence on the crystallization and growth of the perovskite layer as a substrate of the perovskite layer. At present, the inorganic hole transport layer NiO x has a good development prospect due to its superior chemical stability and lower material cost, but the trans perovskite solar cell based on the inorganic hole transport layer NiO x still has a lower highest efficiency than the organic hole transport layer, and the NiO x hole transport layer has a higher surface defect, lower intrinsic low conductivity and energy level mismatch with the perovskite layer, which is the cause of the low efficiency and poor stability of the perovskite solar cell. NiO x is a semiconductor material with intrinsic cation vacancies. During the preparation process, part of the Ni 2+ ions are converted into Ni≥3+ ions. However, the high-valence Ni≥3+ ions on the surface of the NiO x thin film, as a proton acceptor and Lewis electron acceptor, can easily undergo an oxidation-reduction reaction with the organic methylamine and formamidinium cations in the perovskite, thereby decomposing the perovskite to form a thin lead iodide hole extraction barrier, resulting in a decrease in the efficiency and stability of the cell.

[0003] The commonly used methods for passivating the surface defects of the NiO x thin film mainly use organic materials such as poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl] phosphonic acid (MeO-2PACz), which have a good passivation effect, but these organic materials are expensive and have no obvious stability improvement, which is not conducive to application in the production of large-area commercial perovskite solar cells.

[0004] ​Therefore, it is of great significance to find a low-cost and simple method to reduce the surface of the nickel oxide film to passivate the surface defects and change the energy level structure of the nickel oxide film, so as to comprehensively improve the stability and photoelectric performance of the perovskite solar cell. SUMMARY

[0005] In view of the defects of the prior art, the present application relates to a method for inhibiting the oxidation-reduction reaction at the nickel oxide / perovskite interface in a perovskite film, which can improve the stability of a perovskite solar device, and specifically relates to 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 oxidation-reduction method mainly focuses on the solution method, 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 will cause uneven coverage on a large-area substrate (5*5 cm 2 The above) and the reduction vapor method can perfectly solve the problem of uneven coverage in the preparation process of a large-area device. By reducing the content of high-valence nickel ions on the surface of the nickel oxide film through acetone vapor, the oxidation-reduction reaction at the nickel oxide / perovskite interface can be inhibited, and the decomposition rate of the perovskite can be reduced. At the same time, the 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 finally improve the stability of the perovskite film and the photoelectric performance of the device.

[0006] The object of the present application is achieved by the following technical solutions:

[0007] The present application provides a method for inhibiting the oxidation-reduction reaction at the nickel oxide / perovskite interface in a perovskite solar cell, which comprises the following steps:

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

[0009] S2. Placing the base nickel oxide film in acetone vapor to perform a reduction treatment;

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

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

[0012] Preferably, in step S1, the nickel oxide film comprises one of nanocrystalline nickel oxide film, magnetron nickel oxide film, sol-gel nickel oxide film, spray nickel oxide film, and 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 used in the present application has a very low volatilization temperature, is easy to operate at low temperature, and is low in price and mild in reaction with nickel oxide, thus being easy to improve the reaction uniformity. The heating temperature is 40-100℃, preferably 40-60℃. The reduction treatment time is 15-30 min. The reduction treatment of the substrate nickel oxide film by the acetone vapor obtained by heating the acetone solvent can passivate the high-valence nickel ions on the surface of the nickel oxide film. The passivation treatment refers to passivating the surface defects of the nickel oxide and promoting the matching of the interface energy levels of the nickel oxide / perovskite.

[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 heating annealing treatment is performed at a temperature of 100-120℃ for 10-30 min, preferably at 100℃ for 30 min.

[0016] The present application uses the easy-to-operate acetone vapor to passivate the surface defects of the nickel oxide hole transport layer and regulate the energy level structure of the nickel oxide film, and finally realizes the dual purposes of improving the stability of the perovskite film and the photoelectric performance of the corresponding device.

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

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

[0019] (1) The present application uses the acetone vapor to passivate the surface defects of the nickel oxide film, and the raw material is low in price, easy to operate and feasible, and easy to mass-produce;

[0020] (2) The present application aims to inhibit the harmful oxidation-reduction reaction at the buried interface of the perovskite solar cell, and realizes the comprehensive improvement of the performance and stability of the perovskite solar cell;

[0021] (3) The nickel oxide films treated by the method of the present application have good passivation effect, and can effectively improve the photoelectric conversion efficiency of the perovskite solar cell. BRIEF DESCRIPTION OF DRAWINGS

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

[0023] Figure 1 X-ray diffraction pattern of the thin film of NiO in Inventive Example 1 x Optical transmittance plot of the thin film

[0024] Figure 2 Optical transmittance plot of the thin film of NiO in Inventive Example 1 x Optical transmittance plot of the thin film

[0025] Figure 3 Optical transmittance plot of the thin film of NiO in Inventive Example 1 x X-ray photoelectron spectroscopy plot of the thin film

[0026] Figure 4 X-ray photoelectron spectroscopy plot of the thin film of NiO in Inventive Example 1 x Ultraviolet photoelectron spectroscopy plot of the thin film

[0027] Figure 5 Photoluminescence plot of the perovskite thin film in Inventive Example 1

[0028] Figure 6 J-V curve plot of the device obtained in Inventive Example 1

[0029] Figure 7 X-ray diffraction pattern of the thin film of NiO in Inventive Example 1 x

[0030] Figure 8 Optical transmittance plot of the thin film of NiO in Inventive Example 1 x

[0031] Figure 9 X-ray photoelectron spectroscopy plot of the thin film of NiO in Inventive Example 1 x

[0032] Figure 10 Ultraviolet photoelectron spectroscopy plot of the thin film of NiO in Inventive Example 1 x

[0033] Figure 11 Photoluminescence plot of the perovskite thin film in Inventive Example 1

[0034] Figure 12 J-V curve plot of the device obtained in Inventive Example 1

[0035] Figure 13 Structure of the perovskite solar cell device in the present invention. DETAILED DESCRIPTION

[0036] ​​​​The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0037] This invention provides a method for suppressing redox reactions at the nickel oxide / perovskite interface and improving the stability of perovskite solar cells, the method comprising the following steps:

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

[0039] S2. Acetone vapor obtained by heating acetone solvent is used to reduce the nickel oxide film on the substrate to passivate high-valence nickel ions on the nickel oxide surface.

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

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

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

[0043] In step S2, the passivation treatment refers to passivating nickel oxide surface defects and promoting energy level matching at the nickel oxide / perovskite interface using 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 an untreated NiOx hole transport layer, and the method includes the following steps:

[0047] (1) A dense NiO layer approximately 20 nm thick was prepared on an ITO conductive substrate. x Hole transport layer: In this comparative example, the hole transport layer is a nanocrystalline nickel oxide thin film, which is prepared as follows: First, 30 mg / mL of nickel oxide nanocrystalline powder is uniformly dispersed in deionized water. Then, a nickel oxide thin film is obtained by spin coating on a conductive substrate. Finally, a dense and uniform nickel oxide hole transport layer is obtained by annealing at 120°C for 10 minutes.

[0048] (2) Take 50 uL Cs 0.05 FA 0.95 PbI3 perovskite precursor is uniformly dispersed on NiO x substrate and spin-coated to prepare, extracted by chlorobenzene anti-solvent and annealed at 100°C for 30 min to get high quality perovskite film of about 500 nm;

[0049] (3) PCBM, BCP and Ag electrode are prepared on perovskite film in turn to get complete perovskite solar cell device.

[0050] Example 1

[0051] The main difference between this example and Comparative Example 1 is that the step of treating the nickel oxide film with acetone vapor is added, and the method comprises the following steps:

[0052] (1) A dense NiO x hole transport layer of about 20 nm thick is prepared on ITO conductive substrate;

[0053] (2) By placing acetone solvent and NiO x film in a closed petri dish, by increasing the heating temperature to 40°C and keeping for 20 min, Acetone-NiO x hole transport layer is obtained.

[0054] (3) Take 50 uL Cs 0.05 FA 0.95 PbI3 perovskite precursor is uniformly dispersed on NiO x substrate and spin-coated to prepare, extracted by chlorobenzene anti-solvent and annealed at 100°C for 30 min to get high quality perovskite film of about 500 nm;

[0055] (4) PCBM, BCP and Ag electrode are prepared on perovskite film in turn to get complete perovskite solar cell device, the structure is shown as Figure 13 .

[0056] Figure 1 and Figure 2 It is shown that in the comparative example we get a higher crystalline quality of NiO x hole transport layer, while maintaining a higher optical transmittance, allowing more visible light to be absorbed by the perovskite layer to improve the short-circuit current of the perovskite solar device. Figure 7 and Figure 8 It is shown that after the acetone vapor treatment in Example 1, the crystalline quality and optical transmittance of the NiO x hole transport layer do not change significantly, and are well maintained. Figure 3 The NiO xThe XPS spectrum of Ni element of the thin film can be analyzed to obtain the content ratio of Ni 3+ / Ni 2+ is 2.99, while Figure 9 The NiO x thin film of Example 1 is treated by acetone vapor 3+ / Ni 2+ is reduced to 2.27, which indicates that the high-valence nickel ions on the surface of the NiO x thin film are reduced by acetone vapor to passivate the surface defects and inhibit the redox reaction of the nickel oxide / perovskite interface. At the same time, Figure 4 and Figure 10 The UPS spectrum of the NiO x thin film can be calculated to obtain the work function and the valence band energy level position of the NiO x thin film of the comparative example, which are 4.71 and -5.26 eV, respectively. The work function of the NiO x thin film treated by acetone vapor can be increased to 4.76 eV, and the valence band energy level is also moved to a deeper position of -5.33 eV. The change in the energy level structure can make the NiO x hole transport layer and the perovskite layer more energy level matched, improving the extraction and transport ability of the hole carriers. Based on the surface defect passivation and energy level structure regulation of the NiO x thin film treated by acetone vapor, Figure 5 and Figure 11 It is shown that the PL light emission intensity of the perovskite thin film of Example 1 is significantly reduced compared to the PL light emission intensity of the perovskite thin film of Comparative Example 1, which indicates that the NiO x hole transport layer treated by acetone vapor has a better hole extraction ability. Finally Figure 6 It is shown that the open-circuit voltage of the perovskite solar cell device based on Comparative Example 1 is 1.03 V, the short-circuit current density is 25.0 mA / cm 2 , the fill factor is 0.778, and the photoelectric conversion efficiency is 20.07%. Benefiting from the lower surface defects and more matched energy level structure of the NiOxhole transport layer treated by acetone vapor, as shown in Figure 12 , the open-circuit voltage and the fill factor of the perovskite solar cell based on Example 1 are significantly improved, the open-circuit voltage is increased to 1.09 V, the short-circuit current density is 24.8 mA / cm 2 , the fill factor is increased to 0.825, and the final photoelectric conversion efficiency is increased to 22.30%.

[0057] Example 2

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

[0059] Comparative Example 2

[0060] The present comparative example is basically the same as Example 1, except that the step of treating the nickel oxide film with acetone vapor is not used, and instead, an interface modification layer is prepared on the hole transport layer. The specific steps are as follows: first, a dense nickel oxide film is prepared by electron beam evaporation, 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 an interface modification layer by spin coating. Although this method can improve the performance of the overall perovskite solar cell, it is difficult to uniformly prepare the solution method in a large-area substrate. In comparison, the use of acetone, a reducing vapor, in the preparation of a large-area substrate can better reflect the priority of uniform preparation, and the reaction between the vapor method and the nickel oxide film will be more gentle, which can also reflect the priority of uniform reaction.

[0061] The present application has many specific application approaches, and the above description is only a preferred embodiment of the present application. It should be noted that the above examples are only used to illustrate the present application, and are not used to limit the protection scope of the present application. For ordinary skilled persons in the art, several improvements can be made without departing from the principles of the present application, and these improvements should also be considered as the protection scope of the present application.

Claims

1. A method for suppressing redox reactions at the nickel oxide / perovskite interface in perovskite solar cells, characterized in that, The method includes the following steps: S1. Prepare a dense nickel oxide thin film on a conductive substrate; S2. Place the substrate nickel oxide film in acetone vapor to perform a reducing treatment on it; S3. Deposit the perovskite precursor on the reduced nickel oxide film and heat-anneal to obtain the perovskite film.

2. The method as described in claim 1, characterized in that, In step S1, the conductive substrate includes one of ITO and FTO conductive substrates.

3. The method as described in claim 1, characterized in that, In step S1, the nickel oxide film includes one of the following: nanocrystalline nickel oxide film, magnetron nickel oxide film, sol-gel nickel oxide film, sprayed nickel oxide film, and atomic layer deposited nickel oxide film.

4. The method as described in claim 1, characterized in that, In step S2, the reduction treatment takes 15-30 minutes.

5. The method as described in 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℃.

6. The method as described in 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 as described in claim 1, characterized in that, In step S3, the heating annealing treatment is performed at a temperature of 100°C for 30 minutes.

8. A perovskite solar cell device, characterized in that, The perovskite solar cell device is obtained by sequentially fabricating PCBM, BCP, and Ag electrodes on a perovskite thin film obtained by the method described in claim 1.

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