Nickel oxide film and low-temperature preparation method and application thereof

Abstract

The invention discloses a nickel oxide film and a low-temperature preparation method and application thereof, and the preparation method comprises the following steps: dissolving nickel salt in water to obtain a precursor solution; adding a buffering agent into the precursor solution, uniformly stirring, filtering, and adjusting the pH value to obtain a mixed solution; and coating the surface of a substrate with the mixed solution, and irradiating with a UV lamp to obtain the nickel oxide film. According to the method, the large-area nickel oxide film is prepared at low temperature, the process is simple, the film-forming property is good, and the prepared nickel oxide film is uniform, compact, low in preparation cost and high in preparation efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a nickel oxide film and a low-temperature preparation method and application thereof. Background Art

[0002] With the advancement of science and technology, human beings have an increasing demand for energy. Solar-powered, renewable, clean and environmentally friendly perovskite solar cells have the advantages of simple preparation and low-temperature processing, and are considered to be promising candidates for the next generation of photovoltaic cells. Nickel oxide (NiOx), as an inorganic hole transport material, has been widely used in perovskite solar cells due to its low cost and inherent stability.

[0003] However, the low power conversion efficiency and stability of conventional NiOx-based perovskite solar cells are the main obstacles to their commercialization. Most NiOx films prepared by solid-phase methods (vapor deposition, magnetron sputtering, etc.) require high-temperature post-treatment and are difficult to apply to flexible ITO substrates. The process is complex and has high requirements for equipment.

[0004] Conventional liquid phase methods, such as spin coating or blade coating directly using NiOx solution to prepare NiOx film, are simple to process but only suitable for small-area processes. As the membrane size increases, it is difficult to ensure high-quality film formation and form a film with uniform thickness and density, resulting in a decrease in the final efficiency of the battery. Therefore, it is not suitable for large-area preparation.

[0005] Although the chemical bath deposition method reported so far has been proven to be able to prepare large-area NiOx films, its deposition time is relatively long, and only one layer of NiOx can be grown each time. Multiple cleanings are required to remove surface residues. The entire process takes a long time, and the cleaning process is difficult to control. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a nickel oxide film and a low-temperature preparation method and application thereof, so as to realize the preparation of a large-area nickel oxide film at a low temperature, with a simple process and good film-forming properties. The prepared nickel oxide film is uniform and dense, with low preparation cost and high preparation efficiency.

[0007] The present invention provides the following technical solutions: In a first aspect, a low-temperature preparation method of a nickel oxide thin film is provided, comprising the following steps: dissolving nickel salt in water to obtain a precursor solution; Adding a buffer to the precursor solution, stirring evenly, filtering, and adjusting the pH value to obtain a mixed solution; The mixed solution is coated on the surface of the substrate and irradiated with a UV lamp to obtain a nickel oxide film.

[0008] Furthermore, the nickel salt includes one or more of nickel chloride, nickel nitrate, and nickel sulfate.

[0009] Furthermore, the concentration of nickel salt in the precursor solution is 0.01-0.1 mol / L. By controlling the concentration of the precursor solution, the preparation of NiOx films of different thicknesses can be achieved, which is beneficial to the thickness control of perovskite solar cells according to different requirements.

[0010] Furthermore, the buffer includes one or more of triethanolamine, sodium citrate, and urea. The addition of the alkaline buffer can not only form Ni 2+ -Organic ligand complexes ensure that the precursor solution slowly precipitates Ni(OH)2 in the subsequent alkaline environment, and can also regulate the acidity and alkalinity of different nickel source solutions, which is conducive to the formation of uniform and dense NiOx films.

[0011] Furthermore, the molar ratio of nickel ions to buffer in the precursor solution is 2:1, and the deposition rate of Ni(OH)2 can be adjusted by adjusting the proportion of the buffer.

[0012] Furthermore, the filtering method includes: filtering using a 0.22 μm PTFE filter membrane.

[0013] Furthermore, the pH adjusting agent used to adjust the pH value includes one or more of NH4OH, KOH, and NaOH; the pH value of the obtained mixed solution is 8 to 11. By controlling the amount of the alkaline pH adjusting agent added, the rate of formation of divalent nickel precipitation and the morphology of the generated precipitation can be controlled. If the pH value is higher than 12, a large amount of precipitation will be generated in the precursor solution in advance, thereby affecting the uniformity of the nickel oxide film.

[0014] Furthermore, the mixed solution is coated on the surface of the substrate by using one of spin coating, scraper coating and slit coating, and after coating, the remaining solution on the surface is dried by spin drying or air gun blowing.

[0015] Furthermore, the UV lamp irradiation time is 5 to 30 minutes.

[0016] Furthermore, the substrate is rigid ITO / FTO or flexible ITO / FTO.

[0017] In a second aspect, a nickel oxide film is provided, which is prepared by the method described in the first aspect.

[0018] In a third aspect, a method for applying the nickel oxide thin film described in the second aspect in an inverted perovskite solar cell is provided.

[0019] Furthermore, the nickel oxide film is a hole transport layer.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention dissolves a nickel salt in water to obtain a precursor solution, adds a buffer to the precursor solution, stirs it evenly, filters it, and adjusts the pH value to obtain a mixed solution, applies the mixed solution to a substrate surface, and irradiates it with a UV lamp to achieve the preparation of a large-area nickel oxide film at a low temperature (25-50° C.). The process is simple, the film-forming property is good, the prepared nickel oxide film is uniform and dense, the preparation cost is reduced, the preparation efficiency is improved, and it is conducive to the preparation of a large-area solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flow chart of a method for preparing a NiOx thin film at low temperature according to an embodiment of the present invention; Figure 2 These are the microscopic images of NiOx thin films prepared in Example 2 of the present invention and in Comparative Example 1: a-NiOx thin film of Example 2, b-NiOx thin film of Comparative Example 1; Figure 3 It is a current density-voltage characteristic curve diagram of the perovskite battery prepared in Example 2 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0023] Example 1

[0024] This embodiment provides a method for preparing a NiOx thin film. The preparation process is as follows: Figure 1 As shown, the specific steps are: After PI etching, the 5*5 cm flexible ITO substrate was ultrasonically cleaned with deionized water, ethanol and isopropanol for 15 min in sequence, and then dried at 100° C. and naturally cooled to obtain a pretreated flexible ITO substrate for standby use.

[0025] Dissolve 10g NiCl2 in 10ml water, stir well, then add 10g sodium citrate and stir well to obtain NiCl2-sodium citrate solution.

[0026] Dilute 1 g of NH4OH with deionized water to 10 times, slowly add it into the above NiCl2-sodium citrate solution, and monitor the pH value in real time to 9.0 using a pH meter.

[0027] The pretreated flexible ITO substrate was UV-treated for 30 minutes, and a divalent nickel liquid film was prepared by scraping. After standing for 3 minutes, the excess solution was blown dry with an air gun, and then the dry film was transferred to a UV box for treatment for 15 minutes to obtain a NiOx film. The film thickness was detected to be about 17 nm.

[0028] The obtained NiOx film was used as a hole transport layer to prepare an inverted perovskite solar cell, and the performance of the obtained perovskite solar cell was tested.

[0029] Example 2

[0030] This embodiment provides a method for preparing a NiOx thin film, which is different from Embodiment 1 in that the type of organic ligand is changed. The specific steps are as follows: After PI etching, the 5*5 cm flexible ITO substrate was ultrasonically cleaned with deionized water, ethanol and isopropanol for 15 min in sequence, and then dried at 100° C. and naturally cooled to obtain a pretreated flexible ITO substrate for standby use.

[0031] Dissolve 10 g of NiCl2 in 10 ml of water, stir well, then add 12 ml of TEA and stir well to obtain a NiCl2-TEA solution.

[0032] Dilute 1 g of NH4OH with deionized water to 10 times, slowly add it into the above NiCl2-TEA solution, and monitor the pH value in real time to 9.0 using a pH meter.

[0033] The pretreated flexible ITO substrate was UV-treated for 30 minutes, and a divalent nickel liquid film was prepared by scraping. After standing for 3 minutes, the excess solution was blown dry with an air gun, and then the dry film was transferred to a UV box for treatment for 15 minutes to obtain a NiOx film. The film thickness was detected to be about 13 nm.

[0034] The obtained NiOx film was used as a hole transport layer to prepare an inverted perovskite solar cell, and the performance of the obtained perovskite solar cell was tested.

[0035] Example 3

[0036] This embodiment provides a method for preparing a NiOx thin film, which is different from Embodiment 2 in that the source of nickel is changed and the pH of the precursor solution is adjusted. The specific steps are as follows: After PI etching, the 5*5 cm flexible ITO substrate was ultrasonically cleaned with deionized water, ethanol and isopropanol for 15 min in sequence, and then dried at 100° C. and naturally cooled to obtain a pretreated flexible ITO substrate for standby use.

[0037] Dissolve 15 mg Ni(NO3)2 in 10 ml water, stir well, then add 13 ml TEA and stir well to obtain Ni(NO3)2-TEA solution.

[0038] Dilute 1 g of KOH with deionized water to 10 times, slowly add it into the above Ni(NO3)2-TEA solution, and monitor the pH value in real time to 10.0 using a pH meter.

[0039] The pretreated flexible ITO substrate was UV-treated for 30 minutes, and a divalent nickel liquid film was prepared by slit coating. After standing for 5 minutes, the excess solution was blown dry with an air gun, and then the dry film was transferred to a UV box for treatment for 15 minutes to obtain a NiOx film. The film thickness was detected to be about 15 nm.

[0040] The obtained NiOx film was used as a hole transport layer to prepare an inverted perovskite solar cell, and the performance of the obtained perovskite solar cell was tested.

[0041] Example 4

[0042] This embodiment provides a method for preparing a NiOx thin film, which is different from Embodiment 3 in that the UV treatment time is changed. The specific steps are as follows: After PI etching, the 5*5 cm flexible ITO substrate was ultrasonically cleaned with deionized water, ethanol and isopropanol for 15 min in sequence, and then dried at 100° C. and naturally cooled to obtain a pretreated flexible ITO substrate for standby use.

[0043] Dissolve 15 mg Ni(NO3)2 in 10 ml water, stir well, then add 13 ml TEA and stir well to obtain Ni(NO3)2-TEA solution.

[0044] Dilute 1 g of KOH with deionized water to 10 times, slowly add it into the above Ni(NO3)2-TEA solution, and monitor the pH value in real time to 10.0 using a pH meter.

[0045] The pretreated flexible ITO substrate was UV-treated for 30 minutes, and a divalent nickel liquid film was prepared by slit coating. After standing for 5 minutes, the excess solution was blown dry with an air gun, and then the dry film was transferred to a UV box for treatment for 20 minutes to obtain a NiOx film. The film thickness was detected to be about 15nm.

[0046] The obtained NiOx film was used as a hole transport layer to prepare an inverted perovskite solar cell, and the performance of the obtained perovskite solar cell was tested.

[0047] Comparative Example 1 This comparative example uses NiOx powder to obtain a NiOx film by blade coating and drying. The specific steps are as follows: After being etched by P1, a 5*5 cm flexible ITO substrate was ultrasonically cleaned with deionized water, ethanol and isopropanol for 15 min, and then dried at 100° C. and cooled naturally for use.

[0048] NiOx powder was dissolved in deionized water at a concentration of 5 mg / ml.

[0049] The surface of the flexible ITO substrate was UV treated for 30 minutes, and a NiOx liquid film was prepared by scraping with a doctor blade. The excess solution was blown dry with an air gun, and then the dry film was transferred to an oven for annealing for 15 minutes to obtain a NiOx film. The film thickness was detected to be about 12 nm.

[0050] The obtained NiOx film was used as a hole transport layer to prepare an inverted perovskite solar cell, and the performance of the obtained perovskite solar cell was tested.

[0051] Performance comparison (1) By Figure 2 It can be seen that compared with Comparative Example 1, the uniformity and coverage of the NiOx film prepared in Example 2 by slow deposition through the interaction of a divalent nickel source and an organic complex and low-temperature treatment are significantly improved.

[0052] (2) The results of the performance tests on the perovskite solar cells of Examples 1 to 4 and Comparative Example 1 are shown in Table 1 below: Table 1 Performance test results of perovskite solar cells of Examples 1 to 4 and Comparative Example 1

[0053] Depend on Figure 3 As shown in Table 1, compared with Comparative Example 1, Example 1 has an improved filling factor due to the increased coverage of the NiOx film; Example 2 has different battery performance from Example 1 due to the use of different organic ligands, wherein the use of TEA in Example 2 makes the nickel oxide film more compact and uniform, and the open circuit voltage is improved while the filling factor is improved; Compared with Example 2, Example 3 obtains a better solution environment by adjusting the pH value of different precursor solutions; Compared with Example 3, Example 4 increases the NiOx film coverage by changing the UV irradiation treatment time. 3+ 、Ni 2+ The ratio of NiOx to NiOx adjusts the energy level of the NiOx film to make it more compatible with the perovskite layer, thereby obtaining a larger open circuit voltage and higher efficiency.

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low-temperature preparation method for a nickel oxide thin film, characterized in that: The following steps are involved: dissolving nickel salt in water to obtain a precursor solution; Adding a buffer to the precursor solution, stirring evenly, filtering, and adjusting the pH value to obtain a mixed solution; The mixed solution is coated on the surface of the substrate and irradiated with a UV lamp to obtain a nickel oxide film.

2. The low-temperature preparation method of nickel oxide thin film according to claim 1, characterized in that: The nickel salt includes one or more of nickel chloride, nickel nitrate and nickel sulfate.

3. The low-temperature preparation method of nickel oxide thin film according to claim 1, characterized in that: The concentration of nickel salt in the precursor solution is 0.01-0.1 mol / L.

4. The low-temperature preparation method of nickel oxide thin film according to claim 1, characterized in that: The buffer includes one or more of triethanolamine, sodium citrate and urea.

5. The low-temperature preparation method of nickel oxide thin film according to claim 1, characterized in that: The molar ratio of nickel ions to buffer in the precursor solution is 2:

1.

6. The low-temperature preparation method of nickel oxide thin film according to claim 1, characterized in that: The filtering method comprises: filtering with a 0.22 μm PTFE filter membrane.

7. The low-temperature preparation method of nickel oxide thin film according to claim 1, characterized in that: The pH adjusting agent used for adjusting the pH value includes one or more of NH4OH, KOH, and NaOH; the pH value of the obtained mixed solution is 8-11.

8. The low-temperature preparation method of nickel oxide thin film according to claim 1, characterized in that: The irradiation time of the UV lamp is 5 to 30 minutes.

9. A nickel oxide thin film, characterized in that: The method is prepared by any one of claims 1 to 8.

10. Use of the nickel oxide thin film according to claim 9 in an inverse perovskite solar cell.

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