Perovskite film preparation method based on small molecule connecting material, perovskite film and solar cell

Abstract

The invention discloses a method for preparing a perovskite film based on a small molecule connecting material, a perovskite film and a solar cell, and relates to the technical field of solar cells. After forming a self-assembled molecular layer (SAMs) of a small molecule connecting material on the surface of a substrate, an inorganic salt film is prepared, a volatile organic salt solution is coated, and finally decomposed during the annealing process to generate nitrogen gas, which improves the bonding force while passivating the interface and avoids film cracking. At the same time, nitrogen can appropriately expand the pore size of the inorganic lead salt to obtain an inorganic layer skeleton with a loose structure, so that the organic salt can fully penetrate to the bottom, fully convert lead iodide into a perovskite phase, and obtain a high-quality perovskite film, which is conducive to significantly improving the efficiency and stability of the perovskite laminated solar cell.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a method for preparing a perovskite film based on a small molecule connecting material, a perovskite film and a solar cell. Background Art

[0002] Against the backdrop of global climate change, photovoltaic technology has developed rapidly. Perovskite silicon tandem solar cells are considered one of the most promising photovoltaic technologies due to their low cost and high efficiency. In terms of efficiency, the upper limit of the efficiency of single-junction perovskite solar cells exceeds 30%, and the upper limit of the efficiency of perovskite silicon tandem solar cells is expected to be close to 45%.

[0003] However, metal oxide electrodes such as nickel oxide do not match the perovskite lattice, and often crack during long-term stability testing, and the problem of poor interface bonding needs to be solved urgently. The international top journal Science published an article titled "Interfacial toughening with self-assembled monolayers enhances perovskite solar cell reliability". The iodine-terminated self-assembled monolayer (I-SAM) was used as a "molecular glue" to anchor the surface hydroxyl (-OH) on the transparent conductive metal oxide (TCO) to achieve self-assembly. The brittle interface between the perovskite film and the underlying SnO2 electron transport layer (ETL) was greatly toughened. The PCE was improved (up to 21.44%), the hysteresis phenomenon was reduced, and the stability of continuous operation at 1 sun maximum power point (MPP) was improved (it is expected that 80% of the initial PCE will be retained for up to 4000 hours).

[0004] Azide groups are widely used in interface modification of perovskite solar cells. The international journal New Journal of Chemistry published an article titled "Additive engineering with sodium azide material for efficient carbon-based perovskite solar cells". Sodium azide was used as a perovskite additive to promote grain growth and improve efficiency and stability.

[0005] The international journal Journal of Materials Chemistry A published an article titled "A dual functional molecule for perovskite / P3HT interface to achieve stable perovskite solar cells", which uses octylamine azide to cross-link with the transport layer material poly(3-hexylthiophene) (P3HT) to form densely connected sites, thereby improving the efficiency and long-term stability of perovskite cells.

[0006] However, in the two-step process of preparing the perovskite layer, the inorganic skeleton of the perovskite in the solar cell is usually thick (>600nm) and dense, so it cannot fully react with the subsequent organic salt solution, resulting in uneven crystallization and composition distribution of the perovskite film. Therefore, it is necessary to use a variety of strategies to improve the growth quality of the perovskite film to improve the long-term stability of the perovskite solar cell. Summary of the invention

[0007] The purpose of the present invention is to address the deficiencies of the prior art and to provide a method for preparing a perovskite film based on a small molecule connecting material, a perovskite film and a solar cell.

[0008] A method for preparing a perovskite film based on a small molecule connecting material, the method comprising the following steps:

[0009] S1. Cover the N3-SAM material evenly and densely on the conductive glass to form a small molecule connecting material molecular layer;

[0010] S2, preparing an inorganic lead salt layer on the N3-SAM modified surface;

[0011] S3, coating an organic ammonium salt solution on the inorganic salt film;

[0012] S4. Annealing treatment is performed at a high temperature of 150°C for 30 minutes to obtain a well-crystallized perovskite film.

[0013] Furthermore, the N3-SAM material is a small molecule connecting material with an azide group, including: p-azidomethylphenyltrimethoxysilane or 3-(azidopropyl)triethoxysilane.

[0014] Furthermore, the S1 specifically includes: dissolving the N3-SAM material in a mixed solution of isopropanol and deionized water, wherein the volume ratio of isopropanol to deionized water is 95:5; forming a small molecule connecting material on the surface of nickel oxide by spin coating, scraping, slit coating, etc., washing with ethanol after standing for 1 hour, and drying at 50°C for 10 minutes for use.

[0015] Furthermore, the concentration of the N3-SAM material after dissolution is 1 mmol / ml.

[0016] Furthermore, the preparation of the PbI2 inorganic lead salt layer on the N3-SAM modified surface includes: using a thermal evaporation method to evaporate a 500nm PbI2 porous film layer on the N3-SAM film layer at an evaporation rate of 4 angstroms / s.

[0017] Furthermore, the organic ammonium salt solution includes FAI or FABr solution.

[0018] According to another aspect of the specification, a perovskite film is also provided, which is prepared according to the perovskite film preparation method of the present invention.

[0019] According to another aspect of the specification, a solar cell is provided, wherein the solar cell comprises a perovskite film prepared by the method for preparing a perovskite film based on a small molecule connecting material.

[0020] Beneficial effects of the present invention: The present invention uses N3-SAM material as a connecting layer, which has two functions, and can improve the performance and long-term stability of perovskite batteries. N3-SAM material has functional groups such as azide groups, which release nitrogen during the perovskite annealing process, increase the lead iodide gap and promote the complete reaction. The amine group generated at the end can passivate the perovskite interface defects. The prior art only solves the connection and passivation problems, but does not solve the problems of small gaps in the two-step PbI2, difficulty in penetration of ammonium salt solutions, and incomplete reactions. The SAM material of the present invention generates gas, optimizes the two-step perovskite crystallization process, and is innovative. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the process of preparing a perovskite film according to an embodiment of the present invention;

[0022] Figure 2 The chemical structure formula of the small molecule connecting material provided by the embodiment of the present invention;

[0023] Figure 3 Schematic diagram of the action mechanism of the small molecule N3-SAM material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0025] Embodiment 1:

[0026] like Figure 1 As shown, the present invention provides a method for preparing a perovskite film based on a small molecule connecting material, comprising:

[0027] Step 1: uniformly and densely cover the N3-SAM material on the conductive glass to form a small molecule connecting material molecular layer; the N3-SAM material is a small molecule connecting material with an azide group, which needs to have Figure 2 Similar to "p-azidomethylphenyltrimethoxysilane ( Shanghai Myril Biochemical Technology Co., Ltd. Purchase)", "3-(Azidopropyl)triethoxysilane (purchased by Anqing Hecheng New Materials Technology Co., Ltd.)" molecular structure.

[0028] The specific steps include: dissolving N3-SAM material in a mixed solution of isopropanol / deionized water (volume ratio = 95:5), forming a small molecule connecting material on the surface of nickel oxide by spin coating, scraper coating, slit coating, etc., standing for 1 hour, washing with ethanol, and drying at 50°C for 10 minutes before use;

[0029] Step 2: preparing a PbI2 inorganic lead salt layer on the N3-SAM modified surface by evaporation or the like;

[0030] Step 3: coating the FAI organic ammonium salt solution on the inorganic salt film;

[0031] Step 4: Annealing is performed at 150°C for 30 minutes. During the high temperature annealing, the N3-SAM material decomposes to generate gas, which expands the PbI2 pores and allows the organic ammonium salt to fully react to obtain a well-crystallized perovskite film.

[0032] like Figure 3 As shown, the reaction mechanism of the present invention includes: the first step, first the methoxy anchor end generates hydroxyl (-OH) and methanol by hydrolysis, and then dehydrates and condenses with the hanging hydroxyl on the nickel oxide transport layer material, and at the same time, the silicates are dehydrated and condensed to form a dense self-assembled molecular layer. In the second step, during the high-temperature annealing process of the perovskite, the functional group (azido group, -N3) at the other end will release nitrogen, appropriately expand the inorganic lead salt skeleton, reduce the lead iodide reaction residue, and optimize the crystal quality. When the nitrogen is completely released, an amine group (-NH2) will be formed at the end of the SAM, passivating the halogen defects at the perovskite interface, inhibiting non-radiative recombination, and optimizing the battery performance.

[0033] Corresponding to the aforementioned embodiment of a method for preparing a perovskite thin film, the present invention also provides an embodiment of a solar cell.

[0034] Example 2 (Modified NiOx Solar Cell):

[0035] The battery structure is ITO / NiOx / N3-SAM / Perovskite / C60 / BCP / Cu. The ITO glass was ultrasonically cleaned in deionized water, acetone and isopropanol in sequence for 20 minutes each, and then subjected to UV ozone treatment for 15 minutes; a 3.5-inch NiO target was used to sputter a NiO hole transport layer on the substrate, with a radio frequency power of 90W, an Ar atmosphere, a temperature of 150°C, and a 15nm thick NiO layer was sputtered at a rate of 0.2 angstroms / s; a azidomethylphenyltrimethoxysilane solution (dissolved in isopropanol / deionized water, 1mmol / ml) was spin-coated on the NiO film at a speed of 4000rpm for 20s, annealed in air at 50°C for 5min to form a molecular bridging interface, and washed with IPA twice; a 500nm PbI2 porous film layer was evaporated on the N3-SAM film layer by thermal evaporation at an evaporation rate of 4 angstroms / s, and a FAI organic salt isopropanol solution was spin-coated at a speed of 4000rpm for 30s. The film was transferred to a hot plate and annealed in ambient air (35% RH) at 150°C for 30 min. The upper passivation layer was spin-coated with CF3-PACl (1 mg / ml) solution at 4000 rpm for 30 s and annealed at 100°C for 10 min. Finally, C60 (20 nm), BCP (5 nm), and Cu (120 nm) were sequentially evaporated using thermal evaporation, and the battery performance was tested after completion.

[0036] Example 3 (solar cell modified with SnO2):

[0037] The battery structure is ITO / SnO2 / N3-SAM / perovskite / Spiro-OMeTAD / Au. The ITO glass was ultrasonically cleaned in deionized water, acetone and isopropanol for 20 minutes each, and then treated with UV ozone for 15 minutes; the diluted SnO2 nanoparticle solution (2.67wt%) was spin-coated on the substrate at 3000rpm for 30s, and annealed at 150℃ for 30min to form a dense SnO2 electron transport layer (about 30nm). The preparation method of the N3-SAM layer and perovskite is exactly the same as in Example 2; 60mg of Spiro-OMeTAD and additives were dissolved in 700μl of chlorobenzene, and 15.5μl of Li-TFSI solution (520mg / ml in acetonitrile) and 22.5μl of t-BP were added to prepare Spiro-OMeTAD solution. The Spiro-OMeTAD hole transport layer with a thickness of about 300 nm was prepared by spin coating at a speed of 3000 rpm for 30 seconds. Finally, 80 nm of Au was thermally evaporated as an electrode, and the battery performance was tested after completion.

[0038] Example 4 (solar cell realized by changing N3-SAM): the cell structure is ITO / NiOx / N3-SAM / perovskite / C60 / BCP / Cu. The operation is exactly the same as in Example 2, except that "p-azidomethylphenyltrimethoxysilane" is replaced by "3-(azidopropyl)triethoxysilane". The performance is almost the same as in Example 2.

[0039] Example 5 (Perovskite-crystalline silicon tandem cell):

[0040] The cell structure is Ag / ITO / SHJ bottom cell / NiOx / N3-SAM / perovskite / SnO2 / IZO / Ag / MgF2. The silicon heterojunction (SHJ) bottom cell was prepared using n-type double-sided textured silicon wafers (CZ, 4 inches, 1-5Ω resistivity, 260μm thickness). Intrinsic, n-type and p-type hydrogenated amorphous silicon layers were deposited on both sides of the wafer using plasma enhanced chemical vapor deposition (PECVD) technology. The back contact layer of the silicon cell was prepared by sputtering ITO (80nm) and thermally evaporating Ag (150nm). A 3.5-inch NiO target was used to sputter a NiO hole transport layer on the substrate. The RF power was 90W, the Ar atmosphere was at a temperature of 150°C, and a 15nm thick NiO layer was sputtered at a rate of 0.2 angstroms / s. N3-SAM ethanol solution (1mmol / mL) was spin-coated on the NiO film at a speed of 4000rpm for 20s, annealed at 50°C in air for 5min to form a molecular bridging interface, and washed with IPA twice. PbI2 and CsBr were co-evaporated by thermal evaporation, and the evaporation rates of PbI2 and CsBr were 4 angstroms / s and 0.8 angstroms / s, respectively. CF3-PACl (1mg / ml) solution was spin-coated at 4000rpm for 30s and annealed at 100°C for 10min. Subsequently, a 20nm C60 film was deposited by thermal evaporation. Transfer to the ALD system, use tetrakis(dimethylamino)tin(iv) and deionized water as precursors, and deposit 15nm of SnO2 at low temperature (usually 100℃). Sputter 80nm of IZO semi-transparent electrode, and deposit silver grid (100nm). Finally, prepare 100nm of MgF2 anti-reflection layer by electron beam evaporation, and perform performance test after completion.

[0041] Comparative Example 1: (annealing time 20 min): The operation is exactly the same as in Example 2, except that the annealing time is changed to 20 min. Due to incomplete release of nitrogen, the perovskite crystal growth time is insufficient, and the performance is significantly reduced.

[0042] Comparative Example 2: (annealing temperature 180° C.): The operation is exactly the same as in Example 2, except that the annealing temperature is changed to 180° C. The high annealing temperature leads to a faster nitrogen release rate, a deviation in the crystallization effect, and a significant decrease in performance.

[0043] Comparative Example 3: (N3-SAM concentration increased by 1.5 mg / ml): The operation is exactly the same as in Example 1, except that the N3-SAM concentration is increased to 1.5 mg / ml. The increased concentration results in uneven coating of the SAM layer and a slight decrease in performance.

[0044] Comparative Example 4: The operation is exactly the same as that in Example 2, except that the N3-SAM layer is not coated.

[0045] Test method: The voltage-current density (JV) curve of the battery is measured by a digital source meter (Keithley Model 2400) under the irradiation of an AM 1.5G solar simulator (SSF5-3A, Class AAA Solar Simulator, Enlitech) at 100mW / cm2, and the effective test area is 1cm2. The light aging test is completed in a nitrogen-filled glove box. The unpackaged battery is placed in a sealed chamber and illuminated by a continuous white light LED with an intensity of 1 sun (Candlelight System, Switzerland). There is a transparent quartz cover in the sealed chamber. Biased at the maximum power point (MPP) voltage, the PCE is measured once an hour, and the battery test performance summary table is as follows:

[0046]

[0047] Those skilled in the art will readily appreciate other embodiments of the present application after considering the description and practicing the contents disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The description and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0048] It should be understood that the above general description and the detailed description below are only exemplary and explanatory and cannot limit the present application. The present application is not limited to the precise structure described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present application is limited only by the attached claims.

Claims

1. A method for preparing a perovskite film based on a small molecule connecting material, characterized in that: The method comprises the following steps: S1. Cover the N3-SAM material evenly and densely on the conductive glass to form a small molecule connecting material molecular layer; S2, preparing an inorganic lead salt layer on the N3-SAM modified surface; S3, coating an organic ammonium salt solution on the inorganic salt film; S4. Annealing treatment is performed at a high temperature of 150°C for 30 minutes to obtain a well-crystallized perovskite film.

2. A method for preparing a perovskite film based on a small molecule connecting material according to claim 1, characterized in that: The N3-SAM material is a small molecule connecting material with an azide group, including: p-azidomethylphenyltrimethoxysilane or 3-(azidopropyl)triethoxysilane.

3. The method for preparing a perovskite film based on a small molecule connecting material according to claim 1, characterized in that: The S1 specifically includes: dissolving the N3-SAM material in a mixed solution of isopropanol and deionized water, wherein the volume ratio of isopropanol to deionized water is 95:5; forming a small molecule connecting material on the surface of nickel oxide by spin coating, scraper coating, slit coating, etc., washing with ethanol after standing for 1 hour, and drying at 50° C. for 10 minutes for use.

4. The method for preparing a perovskite film based on a small molecule connecting material according to claim 3, characterized in that: The concentration of the N3-SAM material after dissolution is 1 mmol / ml.

5. The method for preparing a perovskite film based on a small molecule connecting material according to claim 1, characterized in that: The method of preparing the inorganic lead salt layer on the surface modified by N3-SAM comprises: using a thermal evaporation method to evaporate a 500nm PbI2 porous film layer on the N3-SAM film layer at an evaporation rate of 4 angstroms / s.

6. The method for preparing a perovskite film based on a small molecule connecting material according to claim 1, characterized in that: The organic ammonium salt solution includes FAI or FABr solution.

7. A perovskite thin film, which is prepared according to the perovskite thin film preparation method of the present invention according to any one of claims 1 to 6.

8. A solar cell, characterized in that: A battery comprises the perovskite thin film according to claim 7.

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