All-inorganic perovskite solar cell and preparation method and solvent system thereof

Abstract

This application provides an all-inorganic perovskite solar cell, its preparation method, and solvent system. The method includes a precursor material for forming the perovskite light-absorbing layer and a perovskite precursor solvent. The perovskite precursor solvent is a mixture of dimethyl sulfoxide, acetonitrile, methoxypropanol, and propanol; the volume ratio of dimethyl sulfoxide, acetonitrile, and methoxypropanol is (8-9):(1-0.5):(1-0.5); the volume of propanol is 2-5% of the total volume of dimethyl sulfoxide, acetonitrile, and methoxypropanol. The prepared perovskite precursor solution is filtered, spin-coated, sprayed with anhydrous diethyl ether, and subjected to gradient annealing to form the cell. The solvent synergistically regulates the solubility, crystallization kinetics, and film quality of the inorganic perovskite precursor solution. The perovskite solar cell prepared based on this solvent system has a simple preparation process, low toxicity, environmental friendliness, and high photoelectric conversion efficiency.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, specifically to an all-inorganic perovskite solar cell, its preparation method, and solvent system. Background Technology

[0002] Inorganic CsPbI3 perovskite materials, composed entirely of inorganic ions, exhibit superior intrinsic thermal and photostability compared to organic-inorganic hybrid perovskites. They are considered ideal wide-bandgap (approximately 1.73 eV) light-absorbing layer materials for constructing long-lasting, stable solar cells, particularly for the top cell of tandem solar cells. Currently, the fabrication of high-efficiency all-inorganic CsPbI3 perovskite solar cells mainly relies on traditional polar aprotic solvent systems, employing two primary pathways: One approach is the traditional route based on highly toxic solvents. This route typically uses N,N-dimethylformamide (DMF) or γ-butyrolactone (GBL) as the main solvent, often with the addition of dimethyl sulfoxide (DMSO) as an auxiliary solvent. DMSO can form stable intermediate adducts with lead halides, which is beneficial for obtaining dense, fully covered films. However, this route has inherent drawbacks: First, solvents such as DMF and GBL are highly toxic, volatile, and difficult to biodegrade, posing significant risks to the health of production personnel and the ecological environment, contradicting the concept of green and sustainable manufacturing. Second, the slow evaporation process of these high-boiling-point solvents makes it difficult to precisely control the crystallization kinetics, easily leading to coarse film crystals, rough surfaces, or pinholes. This not only increases the number of non-radiative recombination centers for charge carriers, reducing photoelectric conversion efficiency, but also provides channels for water and oxygen erosion, further accelerating device degradation. Most importantly, the CsPbI3 thin films prepared based on this type of solvent have a photoactive cubic phase (α phase) that is thermodynamically unstable at room temperature and easily transforms spontaneously into a non-photoactive yellow orthorhombic phase (δ phase), resulting in rapid degradation of device efficiency and extremely poor device stability.

[0003] Secondly, there is the exploration of green solvents. To overcome the toxicity and environmental hazards of traditional solvents, researchers have explored low-toxicity, biodegradable green solvents such as water, ethanol (EtOH), and acetonitrile (ACN). Although these solvents have significant advantages in terms of environmental protection, they face challenges when applied to the CsPbI3 system. For example, solvents such as water and ethanol have poor solubility for precursor salts (such as CsI and PbI2), making it difficult to form a precursor solution of uniform concentration. While solvents such as acetonitrile have certain solubility, their crystallization rate during film formation is too fast and difficult to control. They usually only produce films with poor crystallinity, low coverage, porosity, and poor phase purity, which cannot stabilize the metastable α-CsPbI3 phase. As a result, the photoelectric conversion efficiency of the fabricated devices is much lower than that of devices based on traditional solvents.

[0004] In summary, the existing technologies have the following main drawbacks: First, mainstream high-efficiency preparation methods rely on highly toxic and difficult-to-degrade traditional organic solvents, which do not meet the requirements of green chemistry and safe production. Second, neither traditional solvents nor the green solvents explored so far can stabilize the perovskite phase (α phase) of CsPbI3 under mild process conditions, resulting in insufficient long-term stability of the devices. In addition, when the existing green solvent systems are applied to the preparation of all-inorganic perovskites, it is difficult to achieve the three key requirements of sufficient dissolution of the precursor, regulation of crystallization kinetics during film formation, and high phase purity and microstructure density of the final film. This results in the photoelectric performance of the obtained devices being inferior to that of devices based on traditional solvents, thus creating a contradiction between environmental friendliness and high device performance. Summary of the Invention

[0005] In view of this, this application provides an all-inorganic perovskite solar cell, its preparation method and solvent system, to solve the problems of existing all-inorganic perovskite solar cell preparation relying on highly toxic solvents, insufficient phase stability and uncontrollable crystal quality.

[0006] To achieve the above objectives, this application provides the following technical solution: A solvent system for preparing an all-inorganic perovskite solar cell includes a precursor raw material for forming a perovskite light-absorbing layer and a perovskite precursor solvent. The perovskite precursor solvent is a solvent composed of dimethyl sulfoxide, acetonitrile, methoxypropanol, and propanol. The volume ratio of dimethyl sulfoxide, acetonitrile, and methoxypropanol is (8-9):(1-0.5):(1-0.5). The volume of propanol is 2%-5% of the total volume of dimethyl sulfoxide, acetonitrile, and methoxypropanol.

[0007] Further, the methoxypropanol is 3-methoxypropanol, 2-methoxypropanol, or 1-methoxy-2-propanol.

[0008] Furthermore, the propanol is n-propanol or isopropanol.

[0009] An all-inorganic perovskite solar cell includes a conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode stacked sequentially, wherein the perovskite light-absorbing layer is formed using the aforementioned solvent system.

[0010] A method for fabricating an all-inorganic perovskite solar cell, the specific steps for preparing the perovskite light-absorbing layer are as follows: The precursor raw material is dissolved in the perovskite precursor solvent to form a perovskite precursor solution; The perovskite precursor solution was filtered using an organic needle filter. The filtered perovskite precursor solution was spin-coated onto the upper surface of the electron transport layer, and anhydrous ether was sprayed on before the spin-coating was finished. After spin coating, gradient annealing is performed and the film is naturally cooled to room temperature to obtain an all-inorganic perovskite film, forming a perovskite light-absorbing layer. Furthermore, the precursor raw materials include dimethylamine hydroiodate, lead iodide, and cesium iodide.

[0011] Furthermore, in the step of dissolving the precursor raw materials in the perovskite precursor solvent to form a perovskite precursor solution, dimethylamine hydroiodate and lead iodide are first dissolved in the perovskite precursor solvent, and then cesium iodide is added to obtain an all-inorganic perovskite precursor solution.

[0012] Furthermore, the composition of the perovskite light-absorbing layer is CsPbI3.

[0013] Furthermore, the thickness of the perovskite light-absorbing layer is 400-500 nm.

[0014] Applications of all-inorganic perovskite solar cells in the optoelectronic field.

[0015] The technical advantages of this application are as follows: 1. This application constructs a quaternary solvent system with dimethyl sulfoxide (DMSO) as the main solvent and acetonitrile, methoxypropanol, and propanol as co-solvents. This avoids the use of highly toxic solvents such as DMF and GBL in traditional processes, reducing the risk of toxicity and environmental pollution during production. The strong coordination between DMSO and lead iodide stabilizes the precursor. Multiple co-solvents synergistically regulate the supersaturation, coordination environment, and volatilization kinetics of the solution. Antisolvent extraction technology is used to control the crystallization process of CsPbI3. High-quality perovskite films with uniform grain size, smooth and dense surfaces, and no pinhole defects are prepared, reducing the defect density and non-radiative recombination losses. This solvent system can guide CsPbI3 to directly form a stable, photoactive mixed phase containing β and / or γ phases at lower temperatures, while suppressing the formation of non-perovskite δ phases. The prepared films exhibit excellent intrinsic phase stability, remaining stable over long periods at room temperature, delaying efficiency decay. The improved film quality enhances the long-term operational stability of the device.

[0016] 2. Based on the perovskite thin film with both quality and stability, the prepared all-inorganic perovskite solar cell achieves improved photoelectric conversion efficiency and enhanced overall device performance.

[0017] 3. This method is applicable not only to all-inorganic perovskite solar cells but also to organic-inorganic hybrid perovskite systems, making it widely applicable. The entire preparation process is simple, easy to operate, and has low dependence on specialized equipment. Attached Figure Description

[0018] Figure 1This is a structural diagram of the all-inorganic CsPbI3 perovskite solar cell device prepared in this application; Figure 2 The X-ray diffraction patterns of the perovskite thin films prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c) are shown. Figure 3 These are surface and cross-sectional morphology images of the perovskite thin films prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c); Figure 4 These are atomic force microscopy and Kelvin probe force microscopy images of the perovskite thin films prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c). Figure 5 The colloidal size diagrams are of the perovskite films prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c). Figure 6 The UV-Vis absorption spectra of the perovskite films prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c) are shown. Figure 7 The steady-state photoluminescence spectra and time-resolved photoluminescence spectra of the perovskite thin films prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c) are shown. Figure 8 Stability graphs of the perovskite films prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c); Figure 9 The efficiency stability graphs of the all-inorganic CsPbI3 perovskite solar cells prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c) are shown. Figure 10 The efficiency stability graphs of the all-inorganic CsPbI3 perovskite solar cells prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c) under extreme conditions are shown. Figure 11 The current-voltage curves are for the all-inorganic CsPbI3 perovskite solar cells prepared in Comparative Example 1(a), Comparative Example 2(b), and Example 1(c). Detailed Implementation

[0019] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0020] The method used in this application is to use a mixed liquid of dimethyl sulfoxide, acetonitrile, methoxypropanol and propanol as the solvent for the CsPbI3 perovskite precursor solution, wherein dimethyl sulfoxide is the main solvent and acetonitrile, methoxypropanol and propanol are co-solvents.

[0021] Dimethyl sulfoxide, as a strong coordination solvent, reacts with Pb 2+ A stable intermediate phase is formed, which regulates the crystallization rate; acetonitrile, as a volatile co-solvent, accelerates solvent removal and inhibits the formation of non-perovskite phases; methoxypropanol, due to its moderate polarity and boiling point, significantly improves the wettability of the precursor solution to the substrate and avoids pinholes; propanol, as a green co-solvent, further regulates the solution viscosity and nucleation density.

[0022] A stable intermediate phase is formed by the coordination of dimethyl sulfoxide with PbI2. Combined with the adjustment of supersaturation using acetonitrile, methoxypropanol, and propanol, and antisolvent extraction techniques, precise control of CsPbI3 crystallization kinetics is achieved. By achieving a balance between coordination ability, evaporation rate, and film uniformity using the four solvents in specific ratios, a fully inorganic CsPbI3 perovskite film with high crystallinity, uniform grain size, low defect density, low non-radiative recombination loss, smooth and dense surface, and no pinhole defects is obtained. This results in high open-circuit voltage (Voc), high short-circuit current density (Jsc), and excellent fill factor (FF), leading to the fabrication of highly efficient and stable perovskite solar cells.

[0023] It should be noted that although dimethylamine hydroiodate, as a phase stabilizing additive, contains organic groups, its final product CsPbI3 is a completely inorganic perovskite, so the battery is still a completely inorganic perovskite solar cell.

[0024] To facilitate a full understanding of the green solvent system constructed in this application, the main steps include: Step 1: Cut the FTO conductive glass through zinc powder-hydrochloric acid etching, soak it in potassium dichromate-concentrated sulfuric acid solution and NaOH solution for 24 hours each to remove organic matter and acidic substances, wash it with plenty of water and wipe it clean with anhydrous ethanol, and then ultrasonically clean it for 30 minutes each in deionized water with detergent and deionized water to obtain a clean FTO substrate.

[0025] Step 2: After drying the FTO conductive glass with nitrogen, treat it with ultraviolet ozone for 15 minutes, then immerse it in a TiCl4 ice-water mixture, place it in a 70℃ drying oven and heat it for 40-60 minutes. Then rinse the FTO surface repeatedly with ultrapure water and oxidize it for 6 hours to obtain the titanium dioxide electron transport layer.

[0026] Step 3: After drying the FTO conductive glass with pre-deposited titanium dioxide layer with nitrogen, place it on a 200℃ heating stage for gradient annealing for 20-40 min, and then transfer it to ultraviolet ozone treatment for 15 min.

[0027] Step 4: Weigh 0.173g of dimethylamine hydroiodate and 0.46g of lead iodide and dissolve them in a mixed green solvent composed of dimethyl sulfoxide, acetonitrile, methoxypropanol, and propanol, wherein the volume ratio of dimethyl sulfoxide, acetonitrile, and methoxypropanol is (8-9):(1-0.5):(1-0.5); the volume of propanol is 2-5% of the total volume of dimethyl sulfoxide, acetonitrile, and methoxypropanol. Stir magnetically for 3-5 minutes until the solid is completely dissolved. Then weigh 0.26g of cesium iodide and add it to the above solution, and continue stirring magnetically for 3-5 minutes to form a homogeneous CsPbI3 perovskite precursor solution.

[0028] Step 5: Filter the perovskite precursor solution using an organic syringe filter with a pore size of 0.22 μm.

[0029] Step 6: Add 80 μL of filtered perovskite precursor solution to the titanium dioxide electron transport layer obtained in Step 3 and spread it evenly. Spin coat the film using a spin coater at a speed of 500-1500 r / min for 5-20 s, then accelerate to 3000-5000 r / min for 20-40 s. Finally, spray anhydrous diethyl ether rapidly 15 s before the end of the spin coating to form a dense mesophase film.

[0030] Step 7: After spin coating, perform gradient annealing in air at 110℃ for 5-10 min and 200℃ for 5-10 min to completely transform the mesophase film into the black phase CsPbI3 perovskite film. Allow it to cool naturally to room temperature to obtain a fully inorganic CsPbI3 perovskite film with a thickness of approximately 400-500 nm and a uniform and dense surface, forming a perovskite light absorption layer.

[0031] Step 8: Transfer 50 μL of Spiro-OMeTAD solution and spread it evenly on the surface of the perovskite film. Spin-coat at 4000-6000 r / min for 20-40 s to form a hole transport layer.

[0032] Step 9: Deposit the metal electrode Ag using the thermal evaporation method to obtain the perovskite solar cell.

[0033] Example 1 This embodiment uses a mixed liquid of dimethyl sulfoxide, acetonitrile, 3-methoxypropanol, and n-propanol as the solvent for the CsPbI3 perovskite precursor solution. A stable intermediate phase is formed through the coordination of dimethyl sulfoxide with PbI2. By adjusting supersaturation with acetonitrile, 3-methoxypropanol, and n-propanol, and employing anti-solvent extraction technology, precise control of CsPbI3 crystallization kinetics is achieved. This results in the preparation of an all-inorganic CsPbI3 perovskite thin film with low defect state density, low non-radiative recombination loss, uniform grain size, smooth and dense surface, and no pinhole defects, and its application in a high-efficiency and stable perovskite solar cell. To fully understand the green solvent system constructed in this application, the main steps include: Step 1: Cut the FTO conductive glass through zinc powder-hydrochloric acid etching, soak it in potassium dichromate-concentrated sulfuric acid solution and NaOH solution for 24 hours each to remove organic matter and acidic substances, wash it with plenty of water and wipe it clean with anhydrous ethanol, and then ultrasonically clean it for 30 minutes each in deionized water with detergent and deionized water to obtain a clean FTO substrate.

[0034] Step 2: After drying the FTO conductive glass with nitrogen, treat it with ultraviolet ozone for 15 minutes, then immerse it in a TiCl4 ice-water mixture, place it in a 70℃ drying oven and heat it for 50 minutes. Then rinse the FTO surface repeatedly with ultrapure water and oxidize it for 6 hours to obtain the titanium dioxide electron transport layer.

[0035] Step 3: After drying the FTO conductive glass with pre-deposited titanium dioxide layer with nitrogen, place it on a 200℃ heating stage for gradient annealing for 30 min, and then transfer it to ultraviolet ozone treatment for 15 min.

[0036] Step 4: Weigh 0.173 g of dimethylamine hydroiodate and 0.46 g of lead iodide and dissolve them in a mixed green solvent consisting of 900 μL of dimethyl sulfoxide, 50 μL of acetonitrile, 50 μL of 3-methoxypropanol and 20 μL of n-propanol. Stir magnetically for 5 min until the solid is completely dissolved. Then weigh 0.26 g of cesium iodide and add it to the above solution. Continue stirring magnetically for 5 min to form a homogeneous CsPbI3 perovskite precursor solution.

[0037] Step 5: Filter the perovskite precursor solution using an organic syringe filter with a pore size of 0.22 μm.

[0038] Step 6: Add 80 μL of filtered perovskite precursor solution to the titanium dioxide electron transport layer obtained in step 3 and spread it evenly. Spin coat the film using a spin coater at a speed of 1000 r / min for 15 s, then accelerate to 4000 r / min for 30 s. Finally, spray anhydrous diethyl ether 15 s before the end of the spin coating to form a dense mesophase film.

[0039] Step 7: After spin coating, perform gradient annealing in air at 110℃ for 10 min and 200℃ for 10 min to completely transform the mesophase film into the black phase CsPbI3 perovskite film. Allow it to cool naturally to room temperature to obtain a fully inorganic CsPbI3 perovskite film with a thickness of approximately 400-500 nm and a uniform and dense surface, forming a perovskite light absorption layer.

[0040] Step 8: Transfer 50 μL of Spiro-OMeTAD solution and spread it evenly on the surface of the perovskite film. Spin-coat at 5000 r / min for 30 s to form a hole transport layer.

[0041] Step 9: Deposit the metal electrode Ag using the thermal evaporation method to obtain the perovskite solar cell.

[0042] Example 2 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 800 μL dimethyl sulfoxide, 100 μL acetonitrile, 100 μL 3-methoxypropanol and 50 μL n-propanol.

[0043] The remaining steps are the same as in Example 1.

[0044] Example 3 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 900 μL dimethyl sulfoxide, 30 μL acetonitrile, 50 μL 3-methoxypropanol and 20 μL n-propanol.

[0045] The remaining steps are the same as in Example 1.

[0046] Example 4 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 900 μL dimethyl sulfoxide, 120 μL acetonitrile, 50 μL 3-methoxypropanol and 30 μL n-propanol.

[0047] The remaining steps are the same as in Example 1.

[0048] Example 5 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 900 μL dimethyl sulfoxide, 50 μL acetonitrile, 30 μL 3-methoxypropanol and 20 μL n-propanol.

[0049] The remaining steps are the same as in Example 1.

[0050] Example 6 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 900 μL dimethyl sulfoxide, 50 μL acetonitrile, 120 μL 3-methoxypropanol and 30 μL n-propanol.

[0051] The remaining steps are the same as in Example 1.

[0052] Example 7 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 900 μL dimethyl sulfoxide, 50 μL acetonitrile, 50 μL 3-methoxypropanol and 10 μL n-propanol.

[0053] The remaining steps are the same as in Example 1.

[0054] Example 8 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 900 μL dimethyl sulfoxide, 50 μL acetonitrile, 50 μL 3-methoxypropanol and 60 μL n-propanol.

[0055] The remaining steps are the same as in Example 1.

[0056] Example 9 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 900 μL dimethyl sulfoxide, 50 μL acetonitrile, 50 μL 2-methoxypropanol and 20 μL n-propanol.

[0057] The remaining steps are the same as in Example 1.

[0058] Example 10 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 900 μL dimethyl sulfoxide, 50 μL acetonitrile, 50 μL 1-methoxy-2-propanol and 20 μL n-propanol.

[0059] The remaining steps are the same as in Example 1.

[0060] Example 11 The difference between this embodiment and Embodiment 1 is that: In step 4, the mixed green solvent consists of 900 μL dimethyl sulfoxide, 50 μL acetonitrile, 50 μL 3-methoxypropanol and 20 μL isopropanol.

[0061] The remaining steps are the same as in Example 1.

[0062] Example 12 The difference between this embodiment and Embodiment 1 is that: In step 6, anhydrous ether was not sprayed quickly within 15 seconds before the spin coating was completed.

[0063] The remaining steps are the same as in Example 1.

[0064] Comparative Example 1 In step 4, a CsPbI3 perovskite precursor solution is formed using a single solvent, 1000 μL of dimethyl sulfoxide.

[0065] The remaining steps are the same as in Example 1.

[0066] Comparative Example 2 In step 4, the mixed solvent consists of 900 μL of dimethyl sulfoxide and 100 μL of acetonitrile.

[0067] The remaining steps are the same as in Example 1.

[0068] Comparative Example 3 In step 4, the mixed solvent consists of 900 μL of dimethyl sulfoxide and 100 μL of 3-methoxypropanol.

[0069] The remaining steps are the same as in Example 1.

[0070] Comparative Example 4 In step 4, the mixed solvent consists of 1000 μL of dimethyl sulfoxide and 40 μL of n-propanol.

[0071] The remaining steps are the same as in Example 1.

[0072] Comparative Example 5 In step 4, the mixed solvent consists of 900 μL of dimethyl sulfoxide, 50 μL of acetonitrile, and 50 μL of 3-methoxypropanol.

[0073] The remaining steps are the same as in Example 1.

[0074] Comparative Example 6 In step 4, the mixed solvent consists of 900 μL dimethyl sulfoxide, 100 μL acetonitrile and 20 μL n-propanol.

[0075] The remaining steps are the same as in Example 1.

[0076] Comparative Example 7 In step 4, a mixed solvent from the prior art (Chinese Patent CN117651463A) is used, which consists of 500 μL dimethyl sulfoxide, 500 μL acetonitrile and 15 μL ethanol.

[0077] In step 6, anhydrous ether was not sprayed quickly within 15 seconds before the spin coating was completed.

[0078] The remaining steps are the same as in Example 1.

[0079] like Figure 9 As shown, the test method for long-cycle stability is as follows: In ambient air: Battery devices made with three different solvent systems were placed at room temperature (25°C) and low ambient humidity (RH=10%), and the efficiency was measured every 240 hours for a total of 1440 hours.

[0080] Under extreme conditions: Battery devices made with three different solvent systems were placed under high temperature (85°C) and high ambient humidity (RH=35%) conditions, and the efficiency was measured every 8 hours for a total of 56 hours.

[0081] Experimental principle: This solvent system modulates the crystallization kinetics, ultimately forming a mixed phase dominated by β-CsPbI3 and supplemented by γ-CsPbI3. The mixing entropy (ΔS = 5.70 J·mol⁻¹) was calculated. -1 ·K -1 This indicates that the mixed phase has a higher configurational entropy. The increase in entropy lowers the Gibbs free energy of the system, thereby improving thermodynamic stability and suppressing the transition to the non-photoactive δ phase.

[0082] Compared to DMSO or DMSO / ACN systems, the quaternary solvent significantly accelerated the crystallization of CsPbI3. Simultaneously, it suppressed inactive intermediate phases such as Cs4PbI6, promoting the formation of a purer perovskite phase. Rapid crystallization contributes to the formation of dense, pinhole-free film structures, reducing defects and degradation pathways.

[0083] Increased PbI 3- The concentration of this concentration (redshift in the absorption spectrum) promotes the formation of smaller, more uniform colloidal particles (approximately 1.2 nm). This is beneficial for subsequent uniform nucleation and the formation of dense thin films, reduces non-radiative recombination sites, and improves device stability and efficiency.

[0084] Thin films prepared with quaternary solvents exhibit lower surface roughness (26.3 nm vs. 61.6 nm) and higher surface contact potential (0.43 V vs. 0.23 V), reducing interface defects and carrier recombination, and enhancing the stability of the device under thermal and humid environments.

[0085] The test results are shown in Table 1: Table 1 Characteristics of all-inorganic perovskite solar cells Experimental conclusion: In Examples 3-8, any solvent ratio exceeding the limits specified in this application will disrupt the synergistic effect of the quaternary system, leading to a decrease in device efficiency.

[0086] In Comparative Example 1, using a single DMSO solvent resulted in uncontrollable crystallization kinetics, leading to a perovskite film with a rough surface, numerous pinholes, and low coverage. Furthermore, solvent residue accelerated perovskite degradation. At room temperature, the film spontaneously transforms into the inactive δ-phase (yellow phase), causing material degradation and device failure. Consequently, the perovskite solar cells prepared from this film exhibited low photoelectric conversion efficiency and poor long-term operational stability.

[0087] Comparative Examples 2-6 show some improvement compared to single solvents, but small defects still exist on the film surface, and the grain size uniformity is insufficient, potentially introducing carrier recombination centers. The lack of hydrogen bonding regulation from polyol co-solvents makes it difficult to precisely control the crystallization rate and intermediate phase transformation. Although the δ-phase formation rate is slowed down, it is not completely suppressed, and there is still a risk of phase transition during long-term storage, affecting device lifespan. Therefore, the photoelectric conversion efficiency of perovskite solar cells prepared from these thin films remains low, and their long-term operational stability is insufficient.

[0088] As can be seen from the above examples and comparative examples, the green solvent system provided in this application can synergistically regulate the solubility, crystallization kinetics, and film quality of the inorganic perovskite precursor solution. When the proportions of each component are within the above-mentioned optimal range (such as Examples 1, 2, 9, 10, and 11), the resulting perovskite solar cells are superior to those obtained by deviating from this range (Examples 3-8) or by using other known solvent combinations (Comparative Examples 1-7). Furthermore, anhydrous diethyl ether spraying as a post-treatment step is also indispensable for extracting residual solvents and promoting rapid crystallization of perovskite (Example 12).

[0089] like Figure 2 As shown, two distinct diffraction signals appeared at diffraction angles of approximately 14.2° and 28.6° 2θ. These two diffraction peaks are attributed to the characteristic diffraction of two crystal planes in the CsPbI3 perovskite structure, respectively. Furthermore, by comparison, it was found that the intensity of the characteristic diffraction peaks of the perovskite thin film in Example 1(c) was the highest under the experimental test conditions, indicating that the thin film prepared under the quaternary solvent system of this application has the best crystal quality.

[0090] like Figure 3 As shown, the perovskite film prepared in Example 1(c) exhibits a highly uniform and continuous morphology, with no obvious grain agglomeration, pore aggregation, or local defect regions. Compared with the perovskite films prepared in Examples 1(a) and 1(b), it has the largest average grain size among the three examples, with a size of 525 nm.

[0091] like Figure 4 As shown, the perovskite film prepared in Example 1(c) has Ra=26.3nm, reduced surface roughness, and higher surface potential, indicating that it has more favorable energy level alignment, which can promote carrier extraction and suppress nonradiative recombination.

[0092] like Figure 5 As shown, the perovskite film prepared in Example 1(c) has the smallest peak size of colloidal particles, approximately 1.2 nm, and the corresponding scattering intensity is higher. This confirms that propanol, as an antisolvent or coordination modifier, can regulate the colloidal chemical environment in the precursor solution and inhibit the formation of large-sized colloidal aggregates, laying the foundation for the subsequent preparation of high-quality, uniform perovskite films.

[0093] like Figure 6 As shown, compared with the perovskite films prepared in Comparative Examples 1(a) and 2(b), the critical wavelength (absorption edge) of the absorption spectrum of the perovskite film prepared in Example 1(c) is shifted towards the longer wavelength direction. This change is beneficial to the utilization of long-wavelength photons by the film and can improve the short-circuit current density of the device.

[0094] like Figure 7 As shown, the perovskite film prepared in Example 1(c) exhibits the highest PL emission intensity in this experiment, indicating that the solvent system can effectively passivate defects inside the CsPbI3 film, thereby suppressing nonradiative recombination of charge carriers. Furthermore, the average carrier lifetime of the film is extended, indicating that defect-assisted nonradiative recombination is effectively suppressed, reducing the defect state density inside the film.

[0095] like Figure 8 As shown, the perovskite films prepared in Comparative Examples 1(a) and 2(b) underwent severe decomposition after 420 days of storage, with the black phase transforming into a non-perovskite yellow δ-CsPbI3 phase. In contrast, the perovskite film prepared in Example 1(c) maintained a stable black perovskite phase under the same environmental conditions, demonstrating that the quaternary solvent system of this application can effectively suppress the decomposition of the perovskite phase.

[0096] like Figure 9 As shown, the CsPbI3 perovskite solar cell device prepared in Example 1(c) without encapsulation still maintains an efficiency of 90.3% of the initial value after 1500h; the device prepared in Comparative Example 2(b) can maintain an initial efficiency of 82%; while the device prepared in Comparative Example 1(a) has decreased to 63% of the initial efficiency after 900h.

[0097] like Figure 10 As shown, under more stringent conditions, the PCE of the CsPbI3 perovskite solar cell prepared in Example 1(c) still maintains approximately 80% of its initial efficiency. This indicates that the quaternary solvent system of this application helps improve the device's resistance to air aging and thermal stability, which is beneficial for the long-term stable operation of perovskite solar cells.

[0098] like Figure 11As shown, the CsPbI3 perovskite solar cell device prepared in Example 1(c) has a higher short-circuit current density and open-circuit voltage than the solar cell devices prepared in Example 1(a) and Comparative Example 2(b), indicating that the quaternary solvent system of this application helps to improve the performance and energy density of the solar cell device.

[0099] In summary, the green solvent system and supporting process proposed in this application not only realize the preparation of high-efficiency inorganic perovskite solar cells, but also ensure that the solvents used meet the requirements of green chemistry, avoiding the use of traditional toxic solvents (such as N,N-dimethylformamide).

[0100] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A solvent system for preparing an all-inorganic perovskite solar cell, comprising a precursor material for forming a perovskite light-absorbing layer and a perovskite precursor solvent, characterized in that, The perovskite precursor solvent is a mixture of dimethyl sulfoxide, acetonitrile, methoxypropanol and propanol. The volume ratio of dimethyl sulfoxide, acetonitrile, and methoxypropanol is (8-9):(1-0.5):(1-0.5). The volume of the propanol is 2-5% of the total volume of the dimethyl sulfoxide, acetonitrile, and methoxypropanol.

2. The solvent system for preparing all-inorganic perovskite solar cells according to claim 1, characterized in that, The methoxypropanol is 3-methoxypropanol, 2-methoxypropanol, or 1-methoxy-2-propanol.

3. The solvent system for preparing all-inorganic perovskite solar cells according to claim 1, characterized in that, The propanol is either n-propanol or isopropanol.

4. A fully inorganic perovskite solar cell, comprising a conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode stacked sequentially, characterized in that, The perovskite light-absorbing layer is formed using the solvent system described in claim 1.

5. The method for preparing an all-inorganic perovskite solar cell according to claim 4, characterized in that, The specific steps for preparing the perovskite light-absorbing layer are as follows: The precursor raw material is dissolved in the perovskite precursor solvent to form a perovskite precursor solution; The perovskite precursor solution was filtered using an organic needle filter. The filtered perovskite precursor solution was spin-coated onto the upper surface of the electron transport layer, and anhydrous ether was sprayed on before the spin-coating was finished. After spin coating, the film is subjected to gradient annealing and then naturally cooled to room temperature to obtain an all-inorganic perovskite film, forming a perovskite light-absorbing layer.

6. The method for preparing an all-inorganic perovskite solar cell according to claim 5, characterized in that, The precursor raw materials include dimethylamine hydroiodate, lead iodide, and cesium iodide.

7. The method for preparing an all-inorganic perovskite solar cell according to claim 5, characterized in that, In the step of dissolving the precursor raw material in the perovskite precursor solvent to form a perovskite precursor solution, dimethylamine hydroiodate and lead iodide are first dissolved in the perovskite precursor solvent, and then cesium iodide is added to obtain an all-inorganic perovskite precursor solution.

8. The method for preparing an all-inorganic perovskite solar cell according to claim 5, characterized in that, The perovskite light-absorbing layer is composed of CsPbI3.

9. The method for preparing an all-inorganic perovskite solar cell according to claim 5, characterized in that, The thickness of the perovskite light-absorbing layer is 400-500 nm.

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