High-performance nickel oxide thin film for perovskite solar cell and preparation method of high-performance nickel oxide thin film

Abstract

The invention relates to a high-performance nickel oxide thin film for a perovskite solar cell and a preparation method of the high-performance nickel oxide thin film, and belongs to the technical field of novel solar cells. A novel method for preparing the nickel oxide hole transport layer based on a traditional chemical bath deposition (CBD) process is provided; a novel amino alcohol ligand (triisopropanolamine) is introduced into a precursor solution to form a strongly-combined complex with Ni < 2 + >, slow release of Ni < 2 + > in the in-situ deposition process is promoted, and a continuous and compact Ni (OH) 2 intermediate is formed; the finally obtained low-defect NiOx film is improved in the aspects of coverage, conductivity and hydroxyl number; in order to further improve the hole mobility, metal ions such as Cu < + >, Rb < + > and Li < + > are introduced to perform doping modification on NiOx; by doping the metal ions, the lattice structure of NiOx can be changed, and the hole extraction capability is improved; the generated orbital hybridization phenomenon can also adjust the valence band position, more favorable energy level matching is obtained, and a new research method is provided for the development of an efficient hole transport layer.

Description

Technical Field

[0001] The present invention relates to the technical field of new material solar cells, and in particular to a high-performance nickel oxide thin film for perovskite solar cells and a preparation method thereof. Background Art

[0002] Since the birth of the world's first solar cell at Bell Labs, photovoltaic technology has made remarkable progress. The early solar cells had a photoelectric conversion efficiency (PCE) of only 6%, and subsequently, crystalline silicon solar cells and thin-film solar cells emerged one after another. Currently, the efficiency of perovskite solar cells has reached 27%, which is very close to that of traditional crystalline silicon solar cells. The optoelectronic properties of hole transport materials (HTMs) and electron transport materials (ETMs) have an important impact on the photovoltaic performance and stability of perovskite solar cells. Especially for inverted planar devices (p-i-n structure), the research on hole transport materials has become the current mainstream direction. Traditional organic hole transport materials, such as poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonic acid) (PEDOT:PSS) and polybis(4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA), although they have been widely used in solar cells, due to problems such as band alignment mismatch and hygroscopicity, perovskite solar cells usually exhibit a low open-circuit voltage (VOC) and poor interfacial contact performance. Therefore, selecting and optimizing suitable hole transport materials is crucial for manufacturing efficient, stable, and low-cost perovskite solar cells.

[0003] Thanks to its inherent stability, superior optical transmittance in the visible light spectrum, efficient hole collection ability, and better band alignment with perovskite, NiOx has been widely and continuously studied in inverted perovskite solar cells. However, NiOx thin films still have deficiencies in terms of uniformity, potential distribution, and surface roughness. In the past decade, researchers have used various advanced preparation methods (such as chemical bath deposition, combustion method, pulsed laser deposition (PLD), electron beam deposition, and atomic layer deposition (ALD)) to prepare denser, more compact, and higher-crystallinity NiOx thin films. At the same time, NiOx has been modified by doping (including transition metals, alkali metals, alkaline earth metals, rare earth metals, and multi-metals) and organic molecular functionalization and other strategies to further improve its optoelectronic properties and interfacial characteristics. In recent years, with the remarkable success of chemical bath deposition (CBD) in preparing electron transport layers (ETLs) in formal devices, the preparation of CBD NiOx has also been widely discussed, but the relevant research results show that this process currently faces challenges such as uncontrollable crystal growth rate and unsatisfactory repeatability. If this problem can be solved, a low-cost and easy-to-operate high-performance hole transport layer preparation process will be developed for efficient inverted perovskite solar cells. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides the following technical solutions:

[0005] A high-performance nickel oxide thin film for perovskite solar cells and a preparation method thereof. By using the chemical bath deposition method, NiOx (undoped) and X:NiOx (X = Cu + , Rb + , Li + ) are respectively deposited on FTO conductive glass. The X:NiOx is metal ion-doped NiOx, where X is the element Cu, Rb or Li. The specific preparation method includes the following steps:

[0006] First step, configure a CBD precursor solution (an aqueous nickel nitrate solution added with amino alcohol molecules), and use triisopropanolamine TPA as a ligand. Adjust the pH of the solution to 11 with 10M KOH.

[0007] Second step, add nitrates of three elements (Cu, Rb, Li) to the original CBD precursor solution respectively to configure a new precursor solution, and perform chemical bath deposition; all three elements are doped at a concentration of 5% (molar ratio) of Ni(NO3)2 to configure a new precursor solution.

[0008] Third step, perform Uv-Ozone treatment on the FTO substrate for 15 min. After treatment, immerse it in the new CBD precursor solution, and deposit an intermediate Ni(OH)2 thin film at 50 °C for 45 min. Finally, anneal it at 270 °C to obtain a NiOx or X:NiOx thin film.

[0009] Preferably, in the first step, the pH of the solution is adjusted to 11 with 10M KOH; in the second step, the X nitrate solution is doped at a concentration of 5% molar ratio of Ni(NO3)2.

[0010] Preferably, in the first step, the pH of the solution is adjusted to 11 with 10M KOH; in the second step, the X nitrate solution is doped at a concentration of 5% molar ratio of Ni(NO3)2. A perovskite solar cell prepared by a high-performance nickel oxide thin film, and the specific preparation steps include:

[0011] S1, using FTO conductive glass as a substrate. Before use, the FTO conductive glass is cleaned with detergent, deionized water, acetone and isopropanol to keep it clean, and then the FTO conductive glass is cleaned with ultraviolet ozone for 15 minutes.

[0012] S2, preparation of the hole transport layer: at 50 °C for 40 min, using the chemical bath deposition method, respectively deposit NiO X (undoped) and X:NiO X(X = Cu + , Rb + , Li +) are deposited on the FTO conductive glass; after the chemical bath deposition is completed, the small molecule material MeO-2PACz is uniformly spin-coated on the surface of the FTO conductive glass on which NiO X or X:NiOx is deposited in the glove box to improve the growth quality of the subsequent perovskite film;

[0013] S3, Preparation of the perovskite precursor solution: Add 691.52 mg of PbI2, 232.16 mg of FAI, 11.92 mg of MAI, 12.63 mg of CsCl and 9.56 mg of RbI to 1 ml of DMF:DMSO mixed solvent (DMF:DMSO = 4:1, v / v), stir for 12 h, and prepare the RbCsFAMA-based perovskite solution;

[0014] S4, Preparation of the perovskite layer: Spin-coat the perovskite precursor solution on the surface of the hole transport layer in the glove box, and then place the wet film on a hot stage at 110 °C to anneal to remove the solvent component and crystallize;

[0015] S5, Preparation of the electron transport layer and the electrode: Deposit 20 nm of C60, 6 nm of BCP and 120 nm of Ag on the perovskite layer using a vacuum coater respectively.

[0016] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0017] Based on the intrinsic properties of the material, the present invention uses a chemical bath deposition process to replace the traditional method to prepare the hole transport layer; compared with the traditional method, the chemical bath deposition method can more precisely control the thickness and uniformity of the film, and helps to improve the saturation and integrity of the interface;

[0018] Subsequently, Cu + , Rb + , Li + Three inorganic metal ions are doped, and the three ions are all doped according to the concentration gradients of 1%, 5%, and 10% (mass fraction) of Ni(NO3)2; at the same time, the effects of the growth time (15 min, 30 min, 45 min, 60 min) and growth temperature (40 °C, 50 °C, 60 °C) on the material are studied; the results show that the optimal doping ratio is 5%, the optimal growth temperature is 50 °C, and the optimal growth time is 45 minutes to precisely control the electronic structure and conductivity of the material and improve the performance of the hole transport layer.

[0019] At a light intensity of 100 mW cm -2Under the simulated sunlight AM1.5G irradiation conditions, the best power conversion efficiency (PCE) of the undoped / doped devices can reach 24.25% and 25.54% respectively. Brief Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of the perovskite solar cell of the present invention;

[0021] Figure 2 It is an X-ray diffraction (XRD) pattern of nickel oxide prepared by the chemical bath deposition method with TPA as the ligand, commercial nickel oxide nanoparticles, and NiOx thin film prepared with TEA as the ligand in the present invention;

[0022] Figure 3 It is a valence band and conduction band position diagram of the nickel oxide hole transport layer prepared by the chemical bath deposition method and the commercial nickel oxide nanoparticle hole transport layer in the present invention;

[0023] Figure 4 It is a cross-sectional scanning electron microscope (SEM) image of the perovskite solar cell based on the nickel oxide hole transport layer prepared in the present invention and the control condition (commercial nickel oxide nanoparticles);

[0024] Figure 5 It is a comparison diagram of the I-V curves of the nickel oxide hole transport layer prepared by the chemical bath deposition method and the commercial nickel oxide nanoparticle hole transport layer in the present invention;

[0025] Figure 6 It is a comparison diagram of the J-V curves of the perovskite solar cell based on the nickel oxide hole transport layer prepared in the present invention and the control condition (commercial nickel oxide nanoparticles). Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the 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 creative efforts fall within the protection scope of the present invention.

[0027] Example 1:

[0028] Please refer to Figures 1-6 , a high-performance nickel oxide thin film for perovskite solar cells and its preparation method. Using the chemical bath deposition method, NiOx (undoped) and X:NiOx (X = Cu+, Rb+, Li+) are respectively deposited on FTO conductive glass. The X:NiOx is metal ion-doped NiOx, where X is the element Cu, Rb or Li. The specific preparation method includes the following steps:

[0029] First step: Configure the CBD precursor solution (an aqueous solution of nickel nitrate with amino alcohol molecules added), use triisopropanolamine (TPA) as a ligand, and adjust the pH of the solution to 11 using 10M KOH.

[0030] Second step: Add nitrates of three elements (Cu, Rb, Li) to the original CBD precursor solution respectively to configure a new precursor solution for chemical bath deposition; all three elements are doped at a concentration of 5% (molar ratio) of Ni(NO3)2 to configure a new precursor solution.

[0031] Third step: Perform Uv - Ozone treatment on the FTO substrate for 15 minutes, immerse the treated substrate in the new CBD precursor solution after treatment, deposit to obtain an intermediate Ni(OH)2 thin film under the conditions of 50 °C for 45 minutes, and finally anneal at 270 °C to obtain NiOx or X:NiOx thin film.

[0032] A perovskite solar cell prepared by a high - performance nickel oxide thin film, and the specific preparation steps include:

[0033] S1: Use FTO conductive glass as the substrate. Before use, clean the FTO conductive glass with detergent, deionized water, acetone and isopropanol respectively to keep it clean, and then use ultraviolet ozone to clean the FTO conductive glass for 15 minutes.

[0034] S2: Preparation of the hole - transporting layer: Under the conditions of 50 °C for 40 minutes, use the chemical bath deposition method to deposit NiO X (undoped) and X:NiO X (X = Cu + 、Rb + 、Li +) on the FTO conductive glass respectively; after the chemical bath deposition, spin - coat the small - molecule material MeO - 2PACz evenly on the surface of the FTO conductive glass deposited with NiO X or X:NiOx in the glove box to improve the growth quality of the subsequent perovskite thin film.

[0035] S3: Preparation of the perovskite precursor solution: Add 691.52 mg PbI2, 232.16 mg FAI, 11.92 mg MAI, 12.63 mg CsCl and 9.56 mg RbI to 1 ml of DMF:DMSO mixed solvent (DMF:DMSO = 4:1, v / v), stir for 12 h to prepare the RbCsFAMA - based perovskite solution.

[0036] S4. Preparation of perovskite layer: In a glove box, spin-coat the perovskite precursor solution on the surface of the hole transport layer, and then place the wet film on a hot plate at 110 °C for annealing to remove the solvent component and crystallize;

[0037] S5. Preparation of electron transport layer and electrode: Use a vacuum coater to deposit 20 nm of C60, 6 nm of BCP, and 120 nm of Ag on the perovskite layer respectively.

[0038] In this example, triisopropanolamine (TPA) is added to the CBD precursor solution. Since the carbon atom where the hydroxyl group in TPA is connected to two methyl groups, it is in a more stable ortho environment compared to triethanolamine (TEA), making TPA more likely to 2+ form a coordination with Ni - and form a more stable complex; after adding OH 2+ the strong binding between TPA and Ni - will hinder the binding of OH 2+ with Ni

[0039] Example 2:

[0040] This example is the optimal value of the concentration of doped metal ions and deposition conditions, and the test data are recorded as shown in the following table:

[0041] Table 1 PV parameters of perovskite solar cells prepared at different doping concentrations

[0042]

[0043] Table 2 PV parameters of perovskite solar cells prepared at different deposition temperatures

[0044]

[0045] Table 3 PV parameters of perovskite solar cells prepared at different deposition times

[0046]

[0047] In this example, the introduction of Cu + , Rb + , Li +Three inorganic metal ions were doped, and all three ions were doped at concentration gradients of 1%, 5%, and 10% (mass fraction) of Ni(NO3)2; meanwhile, the effects of the growth time (15 min, 30 min, 45 min, 60 min) and growth temperature (40 °C, 50 °C, 60 °C) on the material were studied; the results showed that the optimal doping ratio was 5%, the optimal growth temperature was 50 °C, and the optimal growth time was 45 minutes to precisely control the electronic structure and conductivity of the material and improve the performance of the hole transport layer.

[0048] Example 3:

[0049] In this example, as shown in the appendix Figure 1 The structure of the perovskite solar cell includes: Glass / FTO / NiOx / MeO-2PACz / Perovskite / C60 / BCP / Ag.

[0050] Example 4:

[0051] In this example, as shown in the appendix Figure 2 The XRD samples were prepared in the laboratory, and the specific process was as follows:

[0052] 1. Prepare the CBD precursor solution (using TEA and TPA as ligands respectively) and adjust the pH of the solution to 11 with KOH;

[0053] 2. Immerse the Uv-Ozone treated FTO substrate in the precursor solution;

[0054] 3. Deposit to obtain the intermediate Ni(OH)2 film under the conditions of 50 °C and 40 min;

[0055] 4. Anneal at 270 °C for two hours to obtain the NiOx film (TEA and TPA samples respectively);

[0056] NP sample:

[0057] 1. Disperse commercial nickel oxide nanoparticles in an aqueous solution and spin-coat them on the Uv-Ozone treated FTO substrate, and remove the moisture by annealing at 110 °C for 20 min;

[0058] 2. Subsequently, send the film to a third-party agency for testing. The equipment used Bruker D8 advance for testing, and the scanning rate was selected as 5° / min and the step size was 0.02 s;

[0059] It is known from X-ray diffraction (XRD) technology that the crystal structure and orientation of the nickel oxide hole transport material prepared by chemical bath deposition are similar to those of commercial nickel oxide nanoparticles, and a hole transport material suitable for preparing perovskite solar cells has been successfully prepared.

[0060] Example 5:

[0061] In this example, as shown in the appendix Figure 3 The positions of the Fermi level and the conduction band top of different nickel oxide hole transport layers were obtained by ultraviolet photoelectron spectroscopy (UPS), and then the optical band gaps of the same nickel oxide hole transport layers were obtained by ultraviolet-visible absorption (UV-vis). Combining the test results, the positions of the conduction band bottoms of different nickel oxide hole transport layers were obtained and plotted; it can be seen from Figure 3 that the valence band and conduction band of the nickel oxide thin film prepared based on TPA are more matched with the valence band and conduction band positions of perovskite, and the aligned energy levels can reduce the energy loss at the interface of perovskite solar cells.

[0062] Example 6:

[0063] In this example, as shown in the appendix Figure 4 It can be seen from the images of cross-sectional scanning electron microscopy (cross-sectional SEM) that the inverted perovskite solar cell prepared based on TPA has fewer disordered crystal grains, shows a flatter cross-section, and at the same time, obvious longitudinal grain boundaries can be seen to be significantly reduced in the vertical direction; the device with the nickel oxide hole transport layer prepared by the present invention has fewer voids, a flatter cross-section, a more ordered grain structure, and reduced longitudinal grain boundaries.

[0064] Example 7:

[0065] In this example, it can be obtained from the appendix Figure 5 that it can be seen from the I-V images that the nickel oxide thin film modified by element doping (Cu + , Rb + ) has higher conductivity.

[0066] In this example, as shown in the appendix Figure 6 When the hole transport layer material is pure NiO x , the open-circuit voltage is concentrated at 1.110 - 1.135 V, and the highest efficiency is about 24%; keeping other conditions basically the same, when doped with Cu, the open-circuit voltage is concentrated at 1.140 - 1.157 V, the efficiency is concentrated at 24% - 25%, and the highest is 25.54%; keeping other conditions basically the same, when doped with Rb, the open-circuit voltage is concentrated at 1.135 - 1.152 V, the efficiency is concentrated at 24% - 25%, and the highest is 25.13%.

[0067] Generally speaking, metal ion doping can effectively improve the efficiency and open-circuit voltage. At the same time, compared with the doping element Rb, Cu has a more significant improvement in the open-circuit voltage and efficiency.

[0068] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing a high-performance nickel oxide thin film, characterized in that, Using the chemical bath deposition method, X:NiOx is deposited on FTO conductive glass. The X:NiOx is metal ion-doped NiOx, where X is the element Cu, Rb, or Li. The specific preparation method includes the following steps: In the first step, a CBD precursor solution is prepared by adding an aqueous nickel nitrate solution containing amino alcohol molecules, and triisopropanolamine (TPA) is used as a ligand. The pH value of the solution is adjusted using KOH. In the second step, an X nitrate solution is added to the original CBD precursor solution to form a new precursor solution. In the third step, the FTO substrate is treated with Uv-Ozone, and after treatment, it is immersed in the new CBD precursor solution to deposit an intermediate Ni(OH)2 film, and finally annealed to obtain an X:NiOx film.

2. The preparation method of a high-performance nickel oxide thin film according to claim 1, characterized in that, In the first step, the pH of the solution is adjusted to 11 using 10M KOH. In the second step, the X nitrate solution is doped at a concentration of 5% molar ratio of Ni(NO3)2.

3. The preparation method of a high-performance nickel oxide thin film according to claim 1, wherein In the third step, the FTO substrate is treated with Uv-Ozone for 15 minutes. The treated FTO substrate is immersed in the precursor solution, and an intermediate Ni(OH)2 film is deposited under the conditions of 50 °C and 45 minutes. Finally, the X:NiOx film is obtained by annealing at 270 °C for two hours.

4. A high-performance nickel oxide film is prepared by the preparation method of a high-performance nickel oxide film according to any one of claims 1-3.

5. A high-performance nickel oxide film according to claim 4 is used for preparing a perovskite solar cell.

6. A perovskite solar cell prepared from a high-performance nickel oxide thin film according to claim 5, characterized in that, The specific preparation steps include: S1, using FTO conductive glass as the substrate. Before use, the FTO conductive glass is cleaned with detergent, deionized water, acetone, and isopropanol to keep it clean, and then the FTO conductive glass is cleaned with ultraviolet ozone for 15 minutes. S2, Preparation of hole transport layer: At 50 °C for 40 min, using chemical bath deposition method, deposit X:NiO X on the FTO conductive glass; after the chemical bath deposition, spin-coat the small molecule material MeO-2PACz uniformly on the surface of the FTO conductive glass deposited with X:NiOx in the glove box to improve the growth quality of the subsequent perovskite film; S3, preparation of the perovskite precursor solution: PbI2, FAI, MAI, CsCl, and RbI are added to a DMF:DMSO mixed solvent and stirred for 12 h to prepare an RbCsFAMA-based perovskite solution. S4, preparation of the perovskite layer: The perovskite precursor solution is spin-coated on the surface of the hole transport layer in a glove box, and then the wet film is placed on a hot stage at 110 °C for annealing to remove the solvent component and crystallize. S5, preparation of the electron transport layer and the electrode: 20 nm of C60, 6 nm of BCP, and 120 nm of Ag are respectively deposited on the perovskite layer using a vacuum coater.

7. The perovskite solar cell according to claim 6, wherein In S3, the amounts of PbI2, FAI, MAI, CsCl, and RbI are 691.52 mg, 232.16 mg, 11.92 mg, 12.63 mg, and 9.56 mg respectively; in the DMF:DMSO mixed solvent, DMF:DMSO = 4:1, and the volume of the DMF:DMSO mixed solvent is 1 ml.

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