A perovskite absorber layer and its preparation method in solar cells

Abstract

This invention provides a perovskite absorber layer, its preparation method, and a solar cell. The preparation method of the perovskite absorber layer includes: depositing an inorganic precursor material on a substrate surface to form an inorganic framework layer; patterning the inorganic framework layer to form a plurality of uniformly distributed recesses on its surface; subsequently depositing an organic precursor material to form an organic photoactivated layer; and then performing a stepped thermal annealing to allow the organic precursor material to diffuse within the recesses to complete hybridization and crystal growth, thereby obtaining the perovskite absorber layer. This invention introduces a recessed structure formed by photolithography or laser processing on the surface of the perovskite inorganic salt layer, providing an effective physical channel for the diffusion and reaction of the organic salt, significantly promoting the uniformity and integrity of the mixing and crystallization process of the organic and inorganic phases.

Description

Technical Field

[0001] This invention belongs to the field of solar cells, and relates to a perovskite absorber layer, its preparation method, and solar cells. Background Technology

[0002] Perovskite solar cells, as a third-generation photovoltaic technology, possess characteristics such as flexibility and lightweight, demonstrating enormous potential in the photovoltaic field. Furthermore, perovskite solar cells exhibit high efficiency, low cost, simple manufacturing processes, a wide spectral absorption range, and maintain high photoelectric conversion efficiency even under low-light conditions. However, current research and development of perovskite solar cells still faces numerous challenges in their fabrication process, limiting their performance improvement and large-scale application.

[0003] In the fabrication process of the perovskite absorber layer in glass-based perovskite solar cells, the mixed crystallization effect of inorganic and organic salts is not ideal, affecting the absorption of light and the generation and transport of charges in the perovskite absorber layer. These problems make it difficult to further improve the photoelectric conversion efficiency of existing glass-based perovskite solar cells, resulting in decreased stability.

[0004] The core bottleneck currently facing glass-based perovskite solar cells lies in the challenge of controlling the crystallization of the perovskite absorber layer. When using vapor deposition to prepare the absorber layer, the dense inorganic salt layer results in an extremely low diffusion coefficient for the organic salt, leading to unreacted regions exceeding 10%. These unreacted phases concentrate at grain boundaries, forming leakage channels, significantly reducing parallel resistance, exacerbating nonradiative recombination, and causing losses in open-circuit voltage and fill factor. Simultaneously, compositional inhomogeneity induces phase separation, disrupting bandgap continuity, affecting carrier transport, and significantly accelerating performance degradation under illumination and electric fields, severely restricting improvements in cell efficiency and long-term stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a perovskite absorber layer, its preparation method, and a solar cell. By controlling the microstructure of the absorber layer, the problem of poor crystallization quality of the mixed inorganic and organic salts in the perovskite absorber layer is solved.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a perovskite absorber layer, the method comprising: evaporating an inorganic precursor material on a substrate surface to form an inorganic framework layer; patterning the inorganic framework layer to form a plurality of uniformly distributed recesses on its surface; subsequently depositing an organic precursor material to form an organic photoactivated layer; and then performing a stepped thermal annealing to allow the organic precursor material to diffuse within the recesses to complete hybridization and crystal growth, thereby obtaining the perovskite absorber layer.

[0008] This invention involves microstructural regulation of the inorganic framework layer of the perovskite absorber to form uniform recesses, allowing inorganic and organic salts to fully mix and crystallize within the recesses. This improves the quality of the perovskite crystals, enhances carrier separation and transport capabilities, and thus increases light absorption efficiency, which is beneficial for improving the photoelectric conversion efficiency of the battery.

[0009] As a preferred embodiment of the present invention, the recessed portion is a groove extending along the length or width direction of the inorganic framework layer, or a hole recessed along the thickness direction of the inorganic framework layer.

[0010] As one embodiment of the present invention, the width or diameter of the recessed portion is 300~550nm, for example, it can be 300nm, 320nm, 350nm, 380nm, 400nm, 430nm, 450nm, 480nm, 500nm, 520nm, 540nm or 550nm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0011] As one embodiment of the present invention, the depth of the recess is 150~300nm, for example, it can be 150nm, 160nm, 180nm, 200nm, 210nm, 220nm, 240nm, 250nm, 260nm, 280nm or 300nm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0012] As one embodiment of the present invention, the distance between two adjacent recesses is 300~500nm, for example, it can be 300nm, 320nm, 350nm, 380nm, 400nm, 420nm, 430nm, 450nm, 460nm, 480nm or 500nm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0013] As one embodiment of the present invention, the total area of ​​the plurality of recesses is 45% to 55% of the area of ​​the inorganic framework layer, for example, it can be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54% or 55%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0014] In one embodiment of the present invention, a plurality of the grooves are arranged sequentially at intervals along the length or width direction of the inorganic frame layer, and a plurality of the holes are distributed in an array on the surface of the inorganic frame layer.

[0015] In one embodiment of the present invention, the thickness of the inorganic framework layer is 1.1 to 1.2 times the thickness of the organic photoactivation layer, for example, it can be 1.10 times, 1.11 times, 1.12 times, 1.13 times, 1.14 times, 1.15 times, 1.16 times, 1.17 times, 1.18 times, 1.19 times or 1.20 times, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0016] As a preferred embodiment of the present invention, the patterning process is performed using photolithography.

[0017] As one embodiment of the present invention, the photolithographic patterning process includes: sequentially applying adhesive, masking, exposing, wet etching, stripping, and cleaning the inorganic framework layer.

[0018] As one embodiment of the present invention, the etching solution used in the wet etching is an aqueous solution of 1.5~3.0wt% acetic acid, or a mixed solution of hydrochloric acid and isopropanol with a volume ratio of 1:(100~200).

[0019] As one embodiment of the present invention, the temperature of the wet etching is 20~30℃, for example, it can be 20℃, 22℃, 25℃, 27℃, 28℃ or 30℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] As one embodiment of the present invention, the wet etching time is 30~100s, for example, it can be 30s, 40s, 50s, 60s, 70s, 80s, 90s or 100s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] As a preferred embodiment of the present invention, the patterning process is performed using laser scanning.

[0022] In one embodiment of the present invention, the laser scanning process uses a laser with an energy of 100 J / cm². 2 105J / cm 2 110J / cm 2 115J / cm 2 120J / cm 2 125J / cm 2 130J / cm 2 135J / cm 2 Or 140J / cm 2 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0023] As one embodiment of the present invention, the pulse width of the laser scanning process is 8~15ns, for example, it can be 8ns, 9ns, 10ns, 11ns, 12ns, 13ns, 14ns or 15ns, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] As one embodiment of the present invention, the scanning speed of the laser scanning process is 4~6m / s, for example, it can be 4.0m / s, 4.3m / s, 4.5m / s, 4.6m / s, 5.0m / s, 5.2m / s, 5.5m / s, 5.8m / s or 6m / s, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0025] As a preferred embodiment of the present invention, the organic precursor material is deposited using slot coating.

[0026] As one embodiment of the present invention, the coating speed of the slit coating is 5~50mm / s, for example, it can be 5mm / s, 10mm / s, 15mm / s, 20mm / s, 25mm / s, 30mm / s, 35mm / s, 40mm / s, 45mm / s or 50mm / s, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0027] As one embodiment of the present invention, the distance between the slit head used in the slit coating and the inorganic framework layer is 100~160μm, for example, it can be 100μm, 110μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm, 155μm or 160μm, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] This invention forms a uniform and defect-free organic salt liquid film by precisely controlling the process parameters of slit coating, reducing interface defects and improving film quality.

[0029] As a preferred embodiment of the present invention, the organic precursor material comprises a formamidinium halide precursor and a binary mixed solvent.

[0030] As one embodiment of the present invention, the concentration of the formamidinium halide precursor in the organic precursor material is 20~60 mg / mL, for example, it can be 20 mg / mL, 23 mg / mL, 25 mg / mL, 30 mg / mL, 35 mg / mL, 40 mg / mL, 45 mg / mL, 46 mg / mL, 50 mg / mL, 53 mg / mL, 55 mg / mL, 58 mg / mL or 60 mg / mL, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] As one embodiment of the present invention, the viscosity of the organic precursor material is 1.0~5.0 cp, for example, it can be 1.0 cp, 1.5 cp, 2.0 cp, 2.5 cp, 3.0 cp, 3.5 cp, 4.0 cp, 4.5 cp or 2.5 cp, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] This invention controls the viscosity of the organic precursor material within the above-mentioned range. On the one hand, it avoids stringing caused by excessively low viscosity, and on the other hand, it prevents uneven coating caused by excessively high viscosity.

[0033] In one embodiment of the present invention, the binary mixed solvent includes isopropanol and N-methylpyrrolidone.

[0034] As one embodiment of the present invention, the volume ratio of isopropanol to N-methylpyrrolidone is (96~98):(2~4), for example, it can be 96:4.0, 96.5:3.5, 97.0:3.0, 97.5:2.5 or 98.0:2.0, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0035] The organic precursor material of the present invention uses the above-mentioned binary mixed solvent, which ensures good solubility of formamidinium halides. Isopropanol has a low boiling point, which can realize the rapid drying of organic precursor materials, while the high-boiling-point N-methylpyrrolidone can moderately delay the drying process, allowing organic salt molecules to diffuse fully in the recessed part, providing a longer annealing window for the mixing and hybridization of organic salt molecules and inorganic salt molecules.

[0036] As one embodiment of the present invention, the inorganic precursor material includes a combination of PbI2, PbBr2 and CsI, or a combination of PbI2 and CsBr.

[0037] As one embodiment of the present invention, the thickness of the inorganic framework layer is 400~500nm, for example, it can be 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, 460nm, 470nm, 480nm, 490nm or 500nm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0038] As one embodiment of the present invention, the molar ratio of organic precursor material to inorganic precursor material in the perovskite absorber layer is (0.95~1.05):1, for example, it can be 0.95:1, 0.96:1, 0.98:1, 1.00:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1 or 1.05:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] As a preferred embodiment of the present invention, the stepped thermal annealing includes a first annealing process and a second annealing process performed sequentially, wherein the temperature of the first annealing process is lower than the temperature of the second annealing process.

[0040] As one embodiment of the present invention, the temperature of the first annealing treatment is 60~80℃, for example, it can be 60℃, 62℃, 65℃, 68℃, 70℃, 73℃, 75℃, 78℃ or 80℃, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0041] As one embodiment of the present invention, the temperature of the second annealing treatment is 90~120°C, for example, it can be 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] As one embodiment of the present invention, the time for the first annealing treatment is 1 to 3 minutes, for example, it can be 1.0 minutes, 1.2 minutes, 1.5 minutes, 1.8 minutes, 2.0 minutes, 2.2 minutes, 2.5 minutes, 2.8 minutes or 3.0 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] As one embodiment of the present invention, the second annealing time is 8 to 15 minutes, for example, it can be 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] As one embodiment of the present invention, the method for preparing the perovskite absorber layer further includes: pre-drying the surface of the organic photoactivated layer before the stepped thermal annealing.

[0045] As one embodiment of the present invention, the pre-drying method includes: purging the surface of the organic photoactivated layer with a drying gas.

[0046] In one embodiment of the present invention, the flow rate of the drying gas is 4.3~5.7m. 3 / min, for example, could be 4.3m 3 / min, 4.4m 3 / min, 4.5m 3 / min, 4.6m 3 / min, 4.7m 3 / min, 4.8m 3 / min, 5.0m 3 / min, 5.1m 3 / min, 5.2m 3 / min, 5.3m 3 / min, 5.4m 3 / min, 5.5m 3 / min, 5.6m 3 / min or 5.7m 3 / min, but not limited to the listed values; other unlisted values ​​within this range also apply.

[0047] As one embodiment of the present invention, the dew point of the dried gas is <-40°C.

[0048] In a second aspect, the present invention provides a perovskite absorber layer, wherein the perovskite absorber layer is prepared by the method for preparing the perovskite absorber layer described in the first aspect.

[0049] Thirdly, the present invention provides a solar cell comprising a conductive substrate, a first carrier transport layer, a perovskite absorber layer, a second carrier transport layer and an electrode layer stacked sequentially, wherein the perovskite absorber layer includes the perovskite absorber layer described in the second aspect.

[0050] As a preferred embodiment of the present invention, a self-assembled monolayer is disposed between the first carrier transport layer and the perovskite absorber layer, and a lithium fluoride passivation layer is disposed between the second carrier transport layer and the perovskite absorber layer.

[0051] In one embodiment of the present invention, a charge barrier layer is further provided between the second carrier transport layer and the electrode layer.

[0052] This invention optimizes the interface between the perovskite absorber layer and the charge carrier transport layers on both sides, forming an upper anchor and lower encapsulation structure, which effectively reduces interface defects, improves energy level matching, and enhances the photoelectric conversion efficiency of the battery.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] (1) The perovskite absorber layer and its preparation method provided by the present invention form a recessed part by microstructure regulation of the inorganic salt framework layer of the solar cell, so that the organic salt diffuses in the recessed part to the surrounding area, realizing the full mixing and hybridization of inorganic salt and organic salt, which significantly improves the crystal quality of the perovskite absorber layer, enhances the light absorption efficiency and carrier separation and transport capabilities, and effectively improves the photoelectric conversion efficiency of the battery.

[0055] (2) The high-quality crystallization in the perovskite absorber layer prepared by the present invention reduces grain boundary defects and unreacted areas, suppresses leakage current, avoids phase separation, thereby enhancing the long-term operating stability of the battery and extending the battery life.

[0056] (3) The preparation process of the present invention is easy to be compatible with existing production lines, has good scalability and industrial application potential, and provides a reliable path for the large-scale manufacturing of perovskite solar cells. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the structure of the solar cell provided in Example 1.

[0058] Figure 2 This is a top view of the recess formed on the surface of the inorganic framework layer in the perovskite absorber layer provided in Example 1.

[0059] Figure 3 This is a top view of the recess formed on the surface of the inorganic framework layer in the perovskite absorber layer provided in Example 8.

[0060] Figure 4 This is a front view of the recess formed on the surface of the inorganic framework layer in the perovskite absorber layer provided in Example 8.

[0061] Wherein, 1-conductive substrate; 2-hole transport layer; 3-self-assembled monolayer; 4-perovskite absorber layer; 5-lithium fluoride passivation layer; 6-electron transport layer; 7-charge barrier layer; 8-electrode layer; 41-inorganic framework layer; 42-organic photoactivation layer; 43-recessed portion. Detailed Implementation

[0062] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0063] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0064] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0065] In one specific embodiment, the present invention provides a method for preparing a perovskite absorber layer, which specifically includes the following steps:

[0066] S1: Inorganic precursor materials are vapor-deposited on the surface of the substrate to form an inorganic framework layer.

[0067] The inorganic precursor material described in this invention includes a combination of PbI2, PbBr2 and CsI in a mass ratio of 36:4:1, or a combination of PbI2 and CsBr in a mass ratio of 36:1.

[0068] The vapor deposition process described in this invention involves heating an evaporation source under high vacuum to vaporize an inorganic precursor material. The gaseous molecules or atoms then travel in a straight line and deposit onto a substrate at a lower temperature, condensing to form a uniform and dense thin film. This invention employs a vapor deposition process to deposit an inorganic framework layer, controlling its thickness within the range of 400-500 nm. This ensures effective light absorption and allows for thorough mixing with subsequent organic salts for crystal growth.

[0069] In fabricating solar cells, the substrate is a conductive substrate with a hole transport layer deposited on it. To optimize the interface between the perovskite absorber layer and the hole transport layer, a self-assembled monolayer (SAM) is introduced between the inorganic salt framework layer and the hole transport layer as a molecular bridge and energy level modulator, constructing an efficient "energy level ladder" that significantly reduces the hole extraction barrier and accelerates the extraction rate. The hole transport layer is made of NiOx. The self-assembled monolayer can be MeO-2PACZ, whose phosphonic acid groups are compatible with NiO. x Strong P–O–Ni chemical bonds form on the surface, achieving robust molecular-level anchoring and enhancing the mechanical and thermal stability of the interface. Simultaneously, the methoxycarbazole group of the MeO-2PACZ molecule extends outward, and its molecular dipole moment effectively reduces the NiO... x The work function of the SAM layer is such that its Fermi level is almost perfectly aligned with the top of the perovskite valence band. The self-assembled monolayer is deposited via thermal evaporation, with a thickness controlled between 0.5 and 1 nm. The SAM layer provides a uniform, low-defect nucleation interface for the subsequent deposition of inorganic precursor materials, promoting the formation of a denser, finer-grained inorganic framework layer, and forming a dual crystallization regulation from top to bottom and bottom to top with the microgroove structure of the upper layer.

[0070] S2: The inorganic framework layer is patterned to form several uniformly distributed recesses on its surface. The recesses can promote the diffusion of subsequent organic salts from inside to the surrounding area, ensuring that the inorganic salts and organic salts can be fully mixed and grow crystals.

[0071] The recessed portion is a groove extending along the length or width direction of the inorganic framework layer, and a plurality of the grooves are arranged sequentially at intervals along the length or width direction of the inorganic framework layer; or the recessed portion is a hole recessed inward along the thickness direction of the inorganic framework layer, and a plurality of the holes are distributed in an array on the surface of the inorganic framework layer.

[0072] The depth of the recess is 150~300nm, which enables the inorganic framework layer to have good light absorption capability, while ensuring sufficient mixing and crystal growth between it and the organic photoactivated layer.

[0073] In this invention, the total area of ​​several recesses is 45% to 55% of the area of ​​the inorganic framework layer.

[0074] The distance between two adjacent recesses is 300~500nm. When the recess is a groove structure, its width is 300~550nm. When the recess is an inwardly recessed hole, its diameter is 300~550nm.

[0075] It should be noted that the groove has a long side extending along the length or width direction of the inorganic framework layer, and a short side extending along the width or length direction of the inorganic framework layer. In this invention, the width refers to the linear length of the short side.

[0076] This invention proposes the following two methods for patterning processing.

[0077] (1) The patterning process is performed by photolithography.

[0078] The photolithographic patterning process includes sequentially applying a resist, masking, exposing, wet etching, stripping, and cleaning to the inorganic framework layer.

[0079] This invention involves coating a photoresist layer onto the surface of an inorganic framework layer, fabricating a mask, and then performing pattern exposure. The desired recessed structure is formed through wet etching. Subsequently, the photoresist and mask are peeled off, and finally, surface residue is removed by cleaning. The wet etching process uses a 1.5–3.0 wt% aqueous solution of acetic acid, or a mixture of hydrochloric acid and isopropanol at a volume ratio of 1:(100–200), at a temperature of 20–30°C, and for a time of 30–100 s. This invention does not specify the exact operating steps and process parameters for the remaining steps; those skilled in the art can adjust them according to actual conditions.

[0080] (2) The patterning process is performed using laser scanning.

[0081] The laser scanning process described in this invention uses a laser with an energy of 100~140 mJ / cm². 2 The pulse width is 8~15ns and the scan speed is 4~6m / s.

[0082] S3: Subsequently, an organic precursor material is deposited on the inorganic framework layer to form an organic photoactivated layer, and the organic precursor material is filled into the recess.

[0083] In this invention, the thickness of the inorganic framework layer is 1.1 to 1.2 times the thickness of the organic photoactivation layer. The molar ratio of the organic precursor material to the inorganic precursor material in the perovskite absorber layer is (0.95 to 1.05):1.

[0084] The deposition process of the organic precursor material adopts slot coating. Compared with conventional spin coating, slot coating technology can prepare large-area, highly uniform films. At the same time, it has a synergistic effect with the micro-recessed structure of the underlying layer, realizing the directional transport and controllable crystallization of the organic salt precursor solution at the microscale.

[0085] Specifically, the slit coating speed is 5~50mm / s, and the matching solution supply rate is 40~60µL / min, ensuring that the organic precursor material can not only completely fill the recess, but also form a uniform and defect-free liquid film on the inorganic framework layer, resulting in a continuous cover layer after subsequent annealing, thereby achieving an ideal thickness ratio between the organic photoactivated layer and the inorganic framework layer.

[0086] The slit coating uses a slit head with a spacing of 100~160μm between it and the inorganic framework layer to form a stable and uniform meniscus, thereby making the film layer uniform and defect-free.

[0087] The organic precursor material used in this invention comprises a formamidinium halide precursor and a binary mixed solvent. Specifically, the binary mixed solvent uses low-boiling-point isopropanol as the main solvent and high-boiling-point N-methylpyrrolidone as the auxiliary solvent, ensuring that the volume ratio of isopropanol to N-methylpyrrolidone is (96~98):(2~4), so that the subsequent annealing and drying rate is within a reasonable range, providing a longer annealing window for the full diffusion and reaction of organic salt molecules in the recessed portion. The concentration of the formamidinium halide precursor in the organic precursor material is 20~60 mg / mL, and the viscosity of the organic precursor material is 1.0~5.0 cp, which is suitable for the stable operation of the slot coating process.

[0088] In this invention, the average grain size of the grains formed by the hybrid growth of organic and inorganic salts is in the range of 1.0~3.0 μm.

[0089] In the fabrication of solar cells, an electron transport layer needs to be formed above the perovskite absorber layer. However, the large number of halogen vacancies and uncoordinated inorganic salt cations on the surface of the perovskite absorber layer easily lead to energy level defects and ion migration. To optimize the interface between the perovskite absorber layer and the electron transport layer, the upper surface of the organic photoactivator layer needs to be passivated. This invention inserts a lithium fluoride film as a multifunctional interface passivation layer between the perovskite absorber layer and the electron transport layer. Lithium ions in the lithium fluoride film have high mobility and can diffuse to the surface of the perovskite absorber layer, interacting with uncoordinated inorganic salt cations and effectively passivating cation defects. At the same time, fluoride ions in the lithium fluoride film can fill halogen vacancies, forming local halogen-fluorine atom bonds with high bond energy, thereby significantly enhancing the surface lattice stability and suppressing the formation and migration of halogen vacancies. In addition, the lithium fluoride film, as a dipole layer, can fine-tune the electronic structure of the perovskite absorber layer surface, optimize its energy level alignment with the electron transport layer, and promote electron extraction. The lithium fluoride film is deposited via a thermal evaporation process, with a thickness controlled between 0.8 and 1.2 nm, achieving effective interface passivation, allowing electrons to pass through efficiently, and avoiding the introduction of large series resistance. Simultaneously, the lithium fluoride film acts as a buffer layer for the electron transport layer deposition, preventing direct physical bombardment or adverse chemical interactions between the electron transport layer material and the perovskite absorber surface.

[0090] S4: After forming the organic photoactivated layer, a step-by-step thermal annealing is performed to allow the organic precursor material to diffuse around the inside of the recess and complete the hybrid crystal growth to obtain the perovskite absorption layer.

[0091] The stepped thermal annealing described in this invention includes a first annealing treatment and a second annealing treatment performed sequentially, wherein the temperature of the first annealing treatment is lower than the temperature of the second annealing treatment. The first annealing treatment completely removes residual solvent and completes the solid-state ion exchange reaction between the organic precursor material and the inorganic precursor material in the recess. The second annealing treatment promotes the further growth of perovskite grains, improves the crystal structure, and ultimately forms a perovskite absorption layer with high crystallinity and low defect density.

[0092] Specifically, the temperature of the first annealing treatment is 60~80℃ and the time is 1~3min; the temperature of the second annealing treatment is 90~120℃ and the time is 8~15min.

[0093] In some embodiments, the surface of the organic photoactivated layer is pre-dried before the stepped thermal annealing to initially remove residual solvent and lock in the film morphology.

[0094] Specifically, the pre-drying method includes: purging the surface of the organic photoactivated layer with a drying gas. The flow rate of the drying gas is 4.3~5.7 m / s. 3 / min, the dew point of the dry gas is <-40℃.

[0095] In another specific embodiment, the present invention provides a perovskite absorber layer, which is prepared by the perovskite absorber layer preparation method described in a specific embodiment.

[0096] The thickness of the inorganic framework layer is 400-500 nm. The depth of the recess is 150-300 nm, and the spacing between two adjacent recesses is 300-500 nm. When the recess is a trench structure, its width is 300-550 nm. When the recess is an inwardly recessed hole, its diameter is 300-550 nm.

[0097] In another specific embodiment, the present invention provides a solar cell comprising a conductive substrate, a first carrier transport layer, a perovskite absorber layer, a second carrier transport layer and an electrode layer stacked sequentially, wherein the perovskite absorber layer includes the perovskite absorber layer described in another specific embodiment.

[0098] In some embodiments, a self-assembled monolayer is disposed between the first carrier transport layer and the perovskite absorber layer to construct an efficient energy level ladder and reduce the carrier extraction barrier. A lithium fluoride passivation layer is disposed between the second carrier transport layer and the perovskite absorber layer. Through the dual-ion passivation mechanism of lithium ions and fluoride ions, non-radiative recombination is effectively suppressed, resulting in a significant improvement in open-circuit voltage.

[0099] Furthermore, a charge-blocking layer is disposed between the second charge carrier transport layer and the electrode layer to achieve charge blocking. The charge-blocking layer is made of SnOx.

[0100] The conductive substrate includes a TCO conductive substrate or an FTO conductive substrate.

[0101] The electrode layer is a silver electrode or an aluminum electrode.

[0102] The present invention also provides a method for preparing the above-mentioned solar cell, which specifically includes the following steps.

[0103] S10: Provide a glass substrate, deposit a conductive layer TCO or FTO on the glass substrate to form a conductive substrate, and clean the conductive substrate to remove surface impurities.

[0104] S20: A first carrier transport layer is deposited on the surface of a conductive substrate using a sputtering deposition process, providing basic support and hole transport channels for subsequent functional layers.

[0105] S30: A self-assembled monolayer is formed on the surface of the first carrier transport layer by thermal evaporation.

[0106] S40: An inorganic precursor material is vapor-deposited on the surface of a self-assembled monolayer to form an inorganic framework layer. Then, a number of uniformly distributed recesses are formed on the surface of the inorganic framework layer by photolithography patterning or laser scanning.

[0107] S50: Subsequently, an organic precursor material is deposited on the inorganic framework layer, and the organic precursor material diffuses in the recess to complete the hybridization and growth of crystals. Then, a step-by-step thermal annealing is performed to obtain a perovskite absorption layer.

[0108] S60: A lithium fluoride passivation layer is formed on the surface of the perovskite absorber layer using a thermal evaporation process. Then, a second carrier transport layer is deposited using an evaporation process, and a charge blocking layer is formed on the second carrier transport layer using atomic layer deposition technology.

[0109] S70: Finally, an electrode layer is deposited on the charge barrier layer to complete the fabrication of the solar cell.

[0110] Example 1

[0111] This embodiment provides a solar cell, such as Figure 1 As shown, the structure includes a conductive substrate, a hole transport layer, a self-assembled monolayer, a perovskite absorber layer, a lithium fluoride passivation layer, an electron transport layer, a charge blocking layer, and an electrode layer, all stacked sequentially. The conductive substrate is a TOC glass substrate. The hole transport layer is NiOx with a thickness of 50 nm. The self-assembled monolayer has a thickness of 0.5 nm. The perovskite absorber layer includes an inorganic framework layer and an organic photoactivator layer, stacked sequentially on the self-assembled monolayer. The inorganic framework layer has a thickness of 400 nm, and the organic photoactivator layer has a thickness of 350 nm. Multiple recesses are uniformly distributed on the surface of the inorganic framework layer, and these recesses form an interlocking connection with the organic photoactivator layer. Figure 2 As shown, the recessed portion consists of trenches along the width direction of the inorganic framework layer, with multiple trenches arranged sequentially at intervals along the length direction of the inorganic framework layer. The trenches are 400 nm wide and 200 nm deep, with a spacing of 400 nm between adjacent trenches. The total area of ​​all trenches distributed in the inorganic framework layer is 50% of the area of ​​the inorganic framework layer. The lithium fluoride passivation layer is 1 nm thick. The electron transport layer is C60 with a thickness of 20 nm. The charge blocking layer is SnOx with a thickness of 15 nm. The electrode layer is a silver electrode with a thickness of 50 nm.

[0112] Example 2

[0113] This embodiment provides a solar cell, which differs from Embodiment 1 in that: the thickness of the inorganic framework layer is 350nm, the width of the recess is 300nm, the depth is 150nm, the spacing between two adjacent recesses is 300nm, and the rest of the structure is the same as that of Embodiment 1.

[0114] Example 3

[0115] This embodiment provides a solar cell, which differs from Embodiment 1 in that: the thickness of the inorganic framework layer is 500nm, the width of the recess is 500nm, the depth is 300nm, the spacing between two adjacent recesses is 500nm, and the rest of the structure is the same as that of Embodiment 1.

[0116] Example 4

[0117] This embodiment provides a solar cell, which differs from Embodiment 1 in that the number of recesses is increased, so that the total area of ​​all trenches distributed in the inorganic frame layer is 60% of the area of ​​the inorganic frame layer, and the rest of the structure is the same as that of Embodiment 1.

[0118] Example 5

[0119] This embodiment provides a solar cell, which differs from Embodiment 1 in that the number of recesses is reduced, so that the total area of ​​all trenches distributed in the inorganic frame layer is 40% of the area of ​​the inorganic frame layer, while the rest of the structure is the same as in Embodiment 1.

[0120] Example 6

[0121] This embodiment provides a solar cell, which differs from Embodiment 1 in that the depth of the grooves distributed in the inorganic framework layer is 100 nm, while the rest of the structure is the same as that in Embodiment 1.

[0122] Example 7

[0123] This embodiment provides a solar cell, which differs from Embodiment 1 in that the depth of the grooves distributed in the inorganic framework layer is 350 nm, while the rest of the structure is the same as that of Embodiment 1.

[0124] Example 8

[0125] This embodiment provides a solar cell, which differs from Embodiment 1 in that: Figure 3 and Figure 4 As shown, the recessed portion uses holes with a diameter of 400 nm, and multiple holes are distributed in a matrix on the inorganic framework layer. The rest of the structure is the same as in Example 1.

[0126] Example 9

[0127] This embodiment provides a method for preparing the solar cell provided in Embodiment 1, which specifically includes the following steps.

[0128] (1) Provide a glass substrate, deposit a conductive layer TCO on the glass substrate to form a conductive substrate, and clean the conductive substrate in sequence with acetone, isopropanol and deionized water to remove surface impurities.

[0129] (2) A first carrier transport layer is deposited on the surface of a conductive substrate using a sputtering coating process. The oxygen-argon ratio during the sputtering coating process is 1:10, and the sputtering power is 150W.

[0130] (3) A self-assembled monolayer is formed on the surface of the first carrier transport layer by thermal evaporation at a rate of 0.2 Å / s.

[0131] (4) Using inorganic salt raw materials of PbI2 and CsBr with a mass ratio of 36:1 as inorganic precursor materials, inorganic precursor materials are vapor-deposited on the surface of self-assembled monolayer to form an inorganic framework layer. Then, photolithography patterning is performed, i.e., the inorganic framework layer is sequentially coated with adhesive, masked, exposed, wet etched, stripped and cleaned to form multiple uniformly distributed trenches on the surface of the inorganic framework layer. The etching solution used in the wet etching is a 2.0wt% acetic acid aqueous solution, the temperature of the wet etching is 25℃ and the time is 60s.

[0132] (5) The organic precursor material FAI is dissolved in a binary mixed solvent composed of isopropanol and N-methylpyrrolidone to obtain an organic precursor solution. The organic precursor solution is deposited on the inorganic framework layer by slit coating, so that the organic precursor material diffuses from the inside of the recess to the outside and forms an organic photoactivated layer on the surface of the inorganic framework layer. The volume ratio of isopropanol to N-methylpyrrolidone in the binary mixed solvent is 98:2, the concentration of formamidinium halide precursor is 45 mg / mL, the viscosity of the organic precursor solution is 1.0~5.0 cp, the slit coating speed is 10 mm / s, and the distance between the slit head and the inorganic framework layer during slit coating is 150 μm.

[0133] (6) Subsequently, a flow rate of 5m was adopted. 3 The surface of the organic photoactivated layer is purged with a dry gas at a flow rate of / min, followed by a first annealing treatment and a second annealing treatment to obtain the perovskite absorber layer. The dew point of the dry gas is <-40℃, the first annealing treatment is performed at 70℃ for 2 min, and the second annealing treatment is performed at 100℃ for 10 min.

[0134] (7) A lithium fluoride passivation layer is formed on the surface of the perovskite absorber layer by vapor deposition, followed by an electron transport layer, and then SnOx is deposited on the electron transport layer by atomic layer deposition technology.

[0135] (8) Finally, silver is deposited on the SnOx layer to form an electrode layer, thus completing the fabrication of the solar cell.

[0136] Example 10

[0137] This embodiment provides a method for preparing the solar cell provided in Embodiment 2, which specifically includes the following steps.

[0138] (1) Provide a glass substrate, deposit a conductive layer TCO on the glass substrate to form a conductive substrate, and clean the conductive substrate in sequence with acetone, isopropanol and deionized water to remove surface impurities.

[0139] (2) A first carrier transport layer is deposited on the surface of a conductive substrate using a sputtering coating process. The oxygen-argon ratio during the sputtering coating process is 1:10, and the sputtering power is 150W.

[0140] (3) A self-assembled monolayer is formed on the surface of the first carrier transport layer by thermal evaporation at a rate of 0.2 Å / s.

[0141] (4) Using inorganic salt raw materials of PbI2, PbBr2 and CsI with a mass ratio of 36:4:1 as inorganic precursor materials, inorganic precursor materials are vapor-deposited on the surface of self-assembled monolayer to form an inorganic framework layer. Then, photolithography patterning is performed, i.e., the inorganic framework layer is sequentially coated with adhesive, masked, exposed, wet etched, stripped and cleaned to form multiple uniformly distributed trenches on the surface of the inorganic framework layer. The etching solution used in the wet etching is a mixed solution of hydrochloric acid and isopropanol with a volume ratio of 1:200. The temperature of the wet etching is 30℃ and the time is 45s.

[0142] (5) The organic precursor material FAI is dissolved in a binary mixed solvent composed of isopropanol and N-methylpyrrolidone to obtain an organic precursor solution. The organic precursor solution is deposited on the inorganic framework layer by slit coating, so that the organic precursor material diffuses from the inside of the recess to the outside and forms an organic photoactivated layer on the surface of the inorganic framework layer. The volume ratio of isopropanol to N-methylpyrrolidone in the binary mixed solvent is 97:3, the concentration of formamidinium halide precursor is 50 mg / mL, the viscosity of the organic precursor solution is 1.0~5.0 cp, the slit coating speed is 20 mm / s, and the distance between the slit head and the inorganic framework layer during slit coating is 160 μm.

[0143] (6) Subsequently, a flow rate of 4.5 m was adopted. 3 The surface of the organic photoactivated layer is purged with a dry gas at a flow rate of / min, followed by a first annealing treatment and a second annealing treatment to obtain the perovskite absorber layer. The dew point of the dry gas is <-40℃, the first annealing treatment is performed at 80℃ for 1 min, and the second annealing treatment is performed at 120℃ for 8 min.

[0144] (7) A lithium fluoride passivation layer is formed on the surface of the perovskite absorber layer by vapor deposition, followed by an electron transport layer, and then SnOx is deposited on the electron transport layer by atomic layer deposition technology.

[0145] (8) Finally, silver is deposited on the SnOx layer to form an electrode layer, thus completing the fabrication of the solar cell.

[0146] Example 11

[0147] This embodiment provides a method for preparing the solar cell provided in Embodiment 3, which specifically includes the following steps.

[0148] (1) Provide a glass substrate, deposit a conductive layer TCO on the glass substrate to form a conductive substrate, and clean the conductive substrate in sequence with acetone, isopropanol and deionized water to remove surface impurities.

[0149] (2) A first carrier transport layer is deposited on the surface of a conductive substrate using a sputtering coating process. The oxygen-argon ratio during the sputtering coating process is 1:10, and the sputtering power is 150W.

[0150] (3) A self-assembled monolayer is formed on the surface of the first carrier transport layer by thermal evaporation at a rate of 0.2 Å / s.

[0151] (4) Using an inorganic salt raw material of PbI2 and CsBr with a mass ratio of 36:1 as an inorganic precursor material, the inorganic precursor material is vapor-deposited on the surface of a self-assembled monolayer to form an inorganic framework layer. Then, multiple uniformly distributed trenches are formed on the surface of the inorganic framework layer by laser scanning treatment. The laser energy used in the laser scanning treatment is 120 mJ / cm 2 The pulse width is 10 ns and the scan speed is 5 m / s.

[0152] (6) The organic precursor material FAI is dissolved in a binary mixed solvent composed of isopropanol and N-methylpyrrolidone to obtain an organic precursor solution. The organic precursor solution is deposited on the inorganic framework layer by slit coating, so that the organic precursor material diffuses from the inside of the recess to the outside and forms an organic photoactivated layer on the surface of the inorganic framework layer. The volume ratio of isopropanol to N-methylpyrrolidone in the binary mixed solvent is 96:4, the concentration of formamidinium halide precursor is 40 mg / mL, the viscosity of the organic precursor solution is 1.0~5.0 cp, the slit coating speed is 30 mm / s, and the distance between the slit head and the inorganic framework layer during slit coating is 100 μm.

[0153] (7) Subsequently, a flow rate of 5.7 m was used. 3 The surface of the organic photoactivated layer is purged with a dry gas at a flow rate of / min, followed by a first annealing treatment and a second annealing treatment to obtain the perovskite absorber layer. The dew point of the dry gas is <-40℃, the first annealing treatment is performed at 60℃ for 3 min, and the second annealing treatment is performed at 110℃ for 12 min.

[0154] (8) A lithium fluoride passivation layer is formed on the surface of the perovskite absorber layer by vapor deposition, followed by an electron transport layer, and then SnOx is deposited on the electron transport layer by atomic layer deposition technology.

[0155] (9) Finally, silver is deposited on the SnOx layer to form an electrode layer, thus completing the fabrication of the solar cell.

[0156] Example 12

[0157] This embodiment provides a method for preparing the solar cell provided in Embodiment 8. The difference between this method and that in Embodiment 9 is that in step (4), a laser scanning process is used to form multiple porous structures, wherein the laser energy used in the laser scanning process is 100 mJ / cm². 2 The pulse width was 8 ns, the scanning speed was 4 m / s, and the remaining steps, raw materials and process parameters were the same as in Example 11.

[0158] Comparative Example 1

[0159] This comparative example provides a solar cell that differs from Example 1 in that no recesses are formed on the inorganic framework layer, while the rest of the structure is the same as in Example 1.

[0160] The electrical performance of the solar cells in Examples 1-8 and Comparative Example 1 was tested, and the results are shown in Table 1. The test conditions were 1000 W / m². 2 , 25°C, AM 1.5G.

[0161] Table 1

[0162]

[0163] Compared to the solar cells of Examples 1-6, the open-circuit voltage and fill factor of the solar cell in Comparative Example 1 are reduced, resulting in a decrease in conversion efficiency. This is mainly because Examples 1-6 form recesses on the inorganic salt layer, allowing the inorganic and organic salts to mix and react fully within the recesses, thus mitigating the loss of open-circuit voltage and fill factor. At the same time, the uniformity of the film layer is improved, thereby enhancing the carrier transport effect and improving the photoelectric conversion efficiency.

[0164] Compared to Example 1, the electrical performance of Examples 4 and 5 deteriorated, mainly due to poor control of the trench size formed on the inorganic framework layer. In Example 4, the trench area was too small, increasing the unreacted areas of organic and inorganic salts, exacerbating interfacial recombination, and causing a decrease in the performance of the perovskite absorber layer. In Example 5, the trench area was too large, resulting in reduced interfacial quality, affecting carrier transport, and thus reducing the electrical performance of the solar cell.

[0165] In Example 6, the trench depth was too small, reducing the diffusion of organic salts around the perimeter of the trench and hindering the thorough mixing of the organic and inorganic phases. This resulted in a decrease in the crystal quality of the perovskite and a reduction in its electrical properties. In Example 7, the trench depth was too large, leading to a decrease in the light absorption capacity of the perovskite absorption layer and poor stability.

[0166] As can be seen from Examples 1 and 8, forming trenches or holes on the inorganic framework layer can promote the reaction between the organic and inorganic phases, thereby improving the electrical performance of the solar cell.

[0167] This invention introduces microgrooves or hole arrays formed by photolithography or laser processing on the surface of perovskite inorganic salt layers to achieve microstructure control. This provides an effective physical channel for the diffusion and reaction of organic salts, significantly promotes the uniformity and integrity of the mixing and crystallization process of organic and inorganic phases, and effectively improves the crystallization quality of perovskite.

[0168] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a perovskite absorber layer, characterized in that, The method for preparing the perovskite absorber layer includes: Inorganic precursor materials are vapor-deposited onto the surface of a substrate to form an inorganic framework layer. The inorganic framework layer is patterned to form a number of uniformly distributed recesses on its surface; Subsequently, an organic precursor material is deposited to form an organic photoactivated layer, followed by stepped thermal annealing, which allows the organic precursor material to diffuse within the recess to complete hybrid crystal growth and obtain the perovskite absorption layer.

2. The method for preparing the perovskite absorber layer according to claim 1, characterized in that, The recessed portion is a groove extending along the length or width direction of the inorganic framework layer, or a hole recessed in the thickness direction of the inorganic framework layer. And / or, the width or diameter of the recess is 300~550nm; And / or, the depth of the recess is 150~300nm; And / or, the distance between two adjacent recesses is 300~500nm; And / or, the total area of ​​the plurality of said recesses is 45% to 55% of the area of ​​the inorganic framework layer; And / or, a plurality of the grooves are arranged sequentially at intervals along the length or width of the inorganic framework layer, and a plurality of the holes are distributed in an array on the surface of the inorganic framework layer.

3. The method for preparing the perovskite absorber layer according to claim 1 or 2, characterized in that, The patterning process is performed using photolithography. And / or, the photolithographic patterning process includes: sequentially applying a resist, masking, exposing, wet etching, stripping, and cleaning the inorganic framework layer; And / or, the etching solution used in the wet etching is an aqueous solution of 1.5~3.0wt% acetic acid, or a mixed solution of hydrochloric acid and isopropanol with a volume ratio of 1:(100~200); And / or, the temperature of the wet etching is 20~30℃; And / or, the wet etching time is 30~100s.

4. The method for preparing the perovskite absorber layer according to claim 1 or 2, characterized in that, The patterning process is performed using laser scanning. And / or, the laser scanning process uses a laser with an energy of 100~140 mJ / cm². 2 ; And / or, the pulse width of the laser scanning process is 8~15ns; And / or, the scanning speed of the laser scanning process is 4~6m / s.

5. The method for preparing the perovskite absorber layer according to claim 1, characterized in that, The organic precursor material was deposited using slot coating. And / or, the coating speed of the slit coating is 5~50mm / s; And / or, the distance between the slit head used in the slit coating and the inorganic framework layer is 100~160μm.

6. The method for preparing the perovskite absorber layer according to claim 5, characterized in that, The organic precursor material comprises a formamidinium halide precursor and a binary mixed solvent; And / or, the concentration of the formamidinium halide precursor in the organic precursor material is 20~60 mg / mL; And / or, the viscosity of the organic precursor material is 1.0~5.0 cp; And / or, the binary mixed solvent includes isopropanol and N-methylpyrrolidone; And / or, the volume ratio of isopropanol to N-methylpyrrolidone is (96~98):(2~4); And / or, the inorganic precursor material includes a combination of PbI2, PbBr2 and CsI, or a combination of PbI2 and CsBr; And / or, the thickness of the inorganic framework layer is 400~500nm; And / or, the molar ratio of organic precursor material to inorganic precursor material in the perovskite absorber layer is (0.95~1.05):

1.

7. The method for preparing the perovskite absorber layer according to claim 1, characterized in that, The stepped thermal annealing includes a first annealing process and a second annealing process performed sequentially, wherein the temperature of the first annealing process is lower than the temperature of the second annealing process. And / or, the temperature of the first annealing treatment is 60~80℃; And / or, the temperature of the second annealing treatment is 90~120℃; And / or, the first annealing process takes 1 to 3 minutes; And / or, the second annealing process takes 8 to 15 minutes; And / or, the method for preparing the perovskite absorber layer further includes: pre-drying the surface of the organic photoactivated layer before the stepped thermal annealing; And / or, the pre-drying method includes: purging the surface of the organic photoactivated layer with a drying gas; And / or, the flow rate of the drying gas is 4.3~5.7m. 3 / min; And / or, the dew point of the dry gas is <-40°C.

8. A perovskite absorber layer, characterized in that, The perovskite absorber layer is prepared by the method described in any one of claims 1-7.

9. A solar cell, characterized in that, The solar cell comprises a conductive substrate, a first carrier transport layer, a perovskite absorber layer, a second carrier transport layer, and an electrode layer stacked sequentially, wherein the perovskite absorber layer comprises the perovskite absorber layer as described in claim 8.

10. The solar cell according to claim 9, characterized in that, A self-assembled monolayer is disposed between the first carrier transport layer and the perovskite absorber layer, and a lithium fluoride passivation layer is disposed between the second carrier transport layer and the perovskite absorber layer. And / or, a charge barrier layer is further provided between the second charge carrier transport layer and the electrode layer.

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