Preparation method of perovskite solar cell based on electron transport layer modification

Abstract

The invention discloses a preparation method of a perovskite solar cell based on electron transport layer modification. The cell sequentially comprises an ITO conductive substrate, a doped conjugated organic acid potassium salt modified tin dioxide electron transport layer, a perovskite light absorption layer and a carbon electrode from bottom to top. During preparation, a modified tin dioxide precursor solution is firstly prepared and spin-coated and annealed to form the electron transport layer, then the perovskite light absorption layer is prepared in an air environment through hot air assisted spin-coating and two-step annealing, and finally, carbon paste is scraped to form the carbon electrode. The oxygen vacancy defect is passivated through coordination of oxygen atoms in the conjugated organic acid potassium salt and tin ions on the surface of tin oxide, a charge transmission channel is constructed by means of a conjugated pi electron system, energy level matching and interface contact quality are optimized, the cell prepared in an air environment still has excellent performance, and the requirements of low-cost and large-scale production are met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solar cells, and particularly relates to a preparation method of a perovskite solar cell based on modification of an electron transport layer. BACKGROUND

[0002] Perovskite solar cells have become a research hotspot in the photovoltaic field due to advantages such as a wide band gap, a high absorption coefficient and low cost. Among them, perovskite solar cells have become a research focus because they do not require an expensive hole transport layer and metal electrode, further reducing the cost.

[0003] However, the existing preparation technology of perovskite cells has the following problems:

[0004] (1) There are defects in the SnO2 electron transport layer, which will become a recombination center for photo-generated carriers, reducing the charge transport efficiency. At the same time, the energy level difference between SnO2 and the all-inorganic perovskite is significant, which hinders the interface charge transport.

[0005] (2) Perovskite is prone to phase transition in the air environment, and the conventional substrate surface has poor wettability, which easily leads to problems such as pinholes and small crystal grains in the perovskite film, further exacerbating carrier recombination and device degradation.

[0006] (3) The existing high-performance carbon-based all-inorganic perovskite solar cells are mostly prepared under inert gas protection, and the device performance and stability are greatly reduced under air environment due to the influence of water and oxygen, which is difficult to meet the needs of large-scale production.

[0007] To solve the above problems, the existing technology mostly uses metal ion doping or inorganic oxide composite to modify SnO2, but such methods are difficult to simultaneously achieve defect passivation, energy level matching and charge transport channel construction. Some schemes also add organic additives to the perovskite precursor to optimize film formation, but this easily introduces insulating phases, affecting charge transport. Therefore, there is an urgent need to develop a technical solution that can simultaneously solve the SnO2 defects, perovskite film formation and air preparation compatibility. SUMMARY

[0008] The application provides a preparation method of a perovskite solar cell based on modification of an electron transport layer, which realizes low-cost preparation of efficient and stable devices in an air environment.

[0009] To achieve the above purpose, the technical solution of the application is as follows:

[0010] A perovskite solar cell based on modification of electron transport layer, from bottom to top, comprises an ITO conductive substrate, a doped conjugated organic acid potassium salt modified tin oxide electron transport layer, a perovskite light absorption layer and a carbon electrode layer; the conjugated organic acid potassium salt is 3-phenyl-2-propenoic acid potassium salt (PC, molecular formula C9H7KO2), the molecular structure contains a conjugated π electron system and a potassium carboxylate functional group, and has the functions of defect passivation and charge transport channel construction; the perovskite light absorption layer is a CsPbI2Br thin film.

[0011] The application further provides a preparation method of the perovskite solar cell, comprising the following steps:

[0012] (1) pretreating the ITO conductive substrate;

[0013] (2) coating the modified tin dioxide solution doped with the conjugated organic acid potassium salt on the ITO conductive substrate, and annealing to obtain the modified tin dioxide electron transport layer.

[0014] (3) coating the CsPbI2Br perovskite precursor solution prepared in advance on the modified electron transport layer by using a hot air flow assisted method, and performing two-step annealing to obtain the perovskite light absorption layer;

[0015] (4) uniformly coating carbon paste on the perovskite light absorption layer by using a doctor blade coating process, and annealing to obtain the perovskite solar cell.

[0016] Further, in step (1), the ITO conductive substrate needs to be cleaned before use, specifically, the ITO conductive substrate is ultrasonically cleaned with a glass cleaner, deionized water, isopropyl alcohol and ethanol, dried, and treated with ozone.

[0017] Further, in step (2), the preparation method of the modified tin dioxide solution is a solution doping method, that is, different concentrations of 3-phenyl-2-propenoic acid potassium salt solution are doped into the diluted tin dioxide solution, and then mixed uniformly to obtain the modified tin dioxide precursor solution.

[0018] Further, in step (2), the 3-phenyl-2-propenoic acid potassium salt solution needs to be formed in a solvent, and a solvent that does not damage the electron transport layer is selected, including ethanol, ethyl acetate and water, the solution concentration is 0.05 mg / ml to 0.25 mg / ml, and after preparation, the solution is left to stand for 12 h to 24 h to wait for the solute to completely dissolve in the solvent; the concentration of the tin dioxide nanoparticle dispersion liquid is 2 wt% to 4 wt%, and the tin dioxide solution with a concentration of 0.2 mol / L is obtained by dilution with deionized water.

[0019] Further, in step (2), the coating amount is 40 μL to 60 μL; the coating method is spin coating, in which the modified tin dioxide precursor solution is dropped onto the ITO conductive substrate and spin-coated at 3000 rpm for 30 s; the annealing is carried out at 150°C for 15 min to 30 min; and the ozone treatment time is 15 min to 20 min.

[0020] Further, in step (3), the preparation of the perovskite precursor solution is as follows: Cesium iodide, lead iodide, and lead bromide are mixed in a molar ratio of 1:0.5:0.5, and the mixed reagents are dissolved in a mixed organic solvent of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF). The mixture is then left to stand in a glove box for 12h to 24h to obtain the CsPbI2Br precursor solution.

[0021] Furthermore, in step (3), the coating method is spin coating, specifically: spin coating for 10 seconds at a rotation speed of 1000 rpm, followed by spin coating for 30 seconds at a rotation speed of 3000 rpm; the hot air flow assisted method is to use a blower perpendicular to the conductive substrate to generate a hot air flow 5 cm to 10 cm directly above the conductive substrate 10 to 20 seconds before the end of spin coating.

[0022] Furthermore, in step (3), the two-step annealing operation is specifically as follows: annealing at a low temperature annealing station at 120°C for 30 seconds, and then quickly transferring to a high temperature annealing station at 250°C to 275°C for 10 minutes.

[0023] Furthermore, in step (4), the coating operation specifically involves: covering the perovskite light-absorbing layer with a strip-shaped mask, and then uniformly coating the carbon paste on it, with the coating thickness controlled at 45μm~50μm; the annealing conditions specifically involve: annealing temperature of 120℃ and annealing time of 20min.

[0024] Compared with the prior art, the present invention has the following technical effects:

[0025] (1) The modified material 3-phenyl-2-acrylate potassium salt was introduced into the SnO2 electron transport layer. The modified material can significantly reduce the carrier recombination center, lower the interfacial charge transport barrier and improve the conductivity, thereby realizing an efficient charge transport channel.

[0026] (2) The surface wettability of the modified tin dioxide is optimized to ensure uniform spreading of the perovskite precursor solution in an air environment.

[0027] (3) The crystallinity of the modified perovskite is improved. The unencapsulated device retains 80.4% of the initial efficiency after being stored in air (RH≈30%) for 340 hours and retains 78.3% of the initial efficiency after being stored in nitrogen environment for 400 hours. The stability is improved by more than 60% compared with the pure SnO2 substrate device, and it exhibits excellent stability in air. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a perovskite solar cell device;

[0029] Figure 2 This is a schematic diagram of the fabrication process of perovskite solar cells.

[0030] Figure 3 The current-voltage characteristic curves of the perovskite solar cell (A) in Example 1, the perovskite solar cell (B1) in Comparative Example 1, the perovskite solar cell (B2) in Comparative Example 2, and the perovskite solar cell (B3) in Comparative Example 3 are shown.

[0031] Figure 4 These are optical microscope images of the degradation process of perovskite films in Example 1 (A) and Comparative Example 1 (B1) under air conditions.

[0032] Figure 5 This is a schematic diagram of the energy level structure of the perovskite light-absorbing layer modified with potassium 3-phenyl-2-acrylate in Example 1. Detailed Implementation

[0033] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1:

[0035] This embodiment uses an ITO conductive substrate / modified tin dioxide electron transport layer / perovskite active layer / carbon electrode as the device structure. Figure 1 ), the specific process for fabricating high-efficiency devices in an air environment ( Figure 2 This includes the following operations:

[0036] (1) Pretreatment of ITO conductive substrate

[0037] (1.1) Cleaning

[0038] Take an ITO conductive substrate with a size of 15mm×15mm, a sheet resistance of 15Ω~25Ω, and a visible light transmittance of more than 80%. Use glass cleaning agent aqueous solution, deionized water, anhydrous ethanol and isopropanol for ultrasonic cleaning in sequence for 15 minutes to remove oil, dust and organic impurities attached to the substrate surface.

[0039] (1.2) Drying and Surface Treatment

[0040] After cleaning, use hot air to blow dry the residual liquid on the substrate surface at a 45° angle to avoid water stains; place the dried ITO conductive substrate in a UV-ozone cleaner for 20 minutes to improve the wettability of the substrate surface and lay the foundation for the uniform film formation of the subsequent electron transport layer.

[0041] (2) Fabrication of electron transport layer

[0042] (2.1) Preparation of modified tin dioxide precursor solution

[0043] A tin dioxide nanoparticle dispersion with a weight ratio of 12 wt% was mixed with deionized water at a volume ratio of 1:2.2, and then mixed for 10 min under magnetic stirring at 600 rpm to obtain a tin dioxide solution with a concentration of 0.2 mol / L.

[0044] Weigh 0.15 mg of potassium 3-phenyl-2-acrylate and dissolve it in 1 mL of ethyl acetate solution. Stir for 12 h to 24 h until completely dissolved to obtain a modified solution with a concentration of 0.15 mg / mL.

[0045] Finally, the modified solution was added dropwise to the diluted tin dioxide solution and mixed evenly to obtain the modified tin dioxide precursor solution, which was then left to stand in the dark for later use.

[0046] (2.2) Spin coating and annealing to form a film

[0047] The pretreated ITO conductive substrate was fixed on the spin coater stage, and 52 μL of modified tin dioxide precursor solution was added. The spin coating parameters were set to 3000 rpm and 30 s to ensure that the solution was evenly spread on the substrate surface. After spin coating, the substrate was immediately transferred to the heating stage and annealed at 150°C for 30 min to 35 min, followed by ozone treatment for 15 min to form a modified SnO2 electron transport layer.

[0048] (3) Preparation of perovskite light-absorbing layer

[0049] (3.1) Preparation of perovskite precursor solution

[0050] 259.81 mg of cesium iodide (CsI), 282.2 mg of lead iodide (PbI2), and 148.3 mg of lead bromide (PbBr2) were weighed out respectively. The above raw materials were mixed with 1 mL of a mixed solvent composed of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) in a 1:1 volume ratio to obtain a mixed system. The mixed system was placed in a 60°C water bath and magnetically stirred at 800 rpm for 2 h until completely dissolved to obtain a CsPbI2Br precursor solution. The solution was stored in a light-protected environment at 25°C and a relative humidity of 30%–40% to prevent degradation of the precursor components.

[0051] (3.2) Thermal assisted spin coating film formation

[0052] Place the ITO conductive substrate on the spin coater platform and add 52 μL of CsPbI2Br precursor solution at a relative humidity of 30%–40%. Then perform a two-step spin coating process: first spin coat at 1000 rpm for 10 s to allow the solution to spread initially, and then spin coat at 3000 rpm for 30 s to accelerate solvent evaporation.

[0053] 20 seconds before the end of the second-stage spin coating process, turn on the adjustable temperature hot air blower and blow the film with hot air at a temperature of 60°C at a distance of 5 cm from the substrate, perpendicular to the air outlet direction, to assist solvent evaporation and suppress the formation of pinhole defects.

[0054] After spin coating, the substrate is immediately subjected to a two-step heat treatment: first, it is transferred to a 120°C heating stage for annealing for 30 seconds, and then transferred to a 265°C heating stage for annealing for 10 minutes to complete the preparation of the perovskite light absorption layer.

[0055] (4) Preparation of carbon electrode

[0056] A patterned A4 paper is used as a mask to cover the surface of the perovskite active layer. This mask defines an effective area of ​​0.225 cm². 2 The electrode pattern is obtained by uniformly coating carbon paste onto the opening area of ​​the mask using a doctor blade. The thickness of the resulting carbon paste layer is controlled to be 45μm to 50μm. After coating, the entire device is placed on a hot stage at 120℃ for annealing for 20 minutes to fully remove volatile solvent components such as terpineol and form a dense carbon electrode. Finally, the mask is removed to obtain a complete perovskite solar cell, denoted as A.

[0057] Comparative Example 1:

[0058] The preparation method of this comparative example is basically the same as that of Example 1, except that: in step (2), no modified material 3-phenyl-2-acrylate potassium salt is added, and the electron transport layer is prepared directly using tin dioxide dispersion. The battery obtained is denoted as B1.

[0059] Comparative Example 2:

[0060] The preparation method of this comparative example is basically the same as that of Example 1, except that the concentration of the modified material 3-phenyl-2-acrylate potassium salt solution in step (2) is 0.05 mg / mL, and the battery obtained is denoted as B2.

[0061] Comparative Example 3:

[0062] The preparation method of this comparative example is basically the same as that of Example 1, except that the concentration of the modified material 3-phenyl-2-acrylate potassium salt solution in step (2) is 0.25 mg / mL, and the battery obtained is denoted as B3.

[0063] Comparative Example 4:

[0064] The preparation method of this comparative example is basically the same as that of Example 1, except that in step (2), the non-conjugated molecule 3-phenylpropionic acid (3-PPA) is used instead of potassium 3-phenyl-2-acrylate (PC), and the concentration of the 3-phenylpropionic acid is 0.15 mg / mL. The battery obtained is designated as B4.

[0065] Test Example 1:

[0066] To systematically evaluate the impact of PC modifier concentration on device performance, key photoelectric parameters, including open-circuit voltage (V), were tested on the perovskite solar cells prepared in the above examples. OC ), short-circuit current density (J SC The results of the fill factor (FF) and power conversion efficiency (PCE) are summarized in Table 1.

[0067] Table 1. Effect of PC modification concentration on the performance of perovskite solar cells.

[0068]

[0069] Data analysis shows that the introduction of the modifier has a significant impact on device performance. When the PC concentration is 0.15 mg / mL, all performance parameters of the device reach their optimal values, achieving V... OC J SC The synergistic effect with FF resulted in a peak photoelectric conversion efficiency of 12.83%. In contrast, devices with PC concentrations deviating from this value or without added PC modifiers did not achieve the same overall performance.

[0070] Figure 3 The figure shows the current-voltage characteristic curves of the perovskite solar cell (A) in Example 1, the perovskite solar cell (B1) in Comparative Example 1, the perovskite solar cell (B2) in Comparative Example 2, and the perovskite solar cell (B3) in Comparative Example 3 of the present invention. This figure quantitatively verifies the optimal concentration value of the PC modifier.

[0071] Test Example 2:

[0072] Long-term stability tests were conducted on the perovskite solar cells prepared in Example 1 and Comparative Examples 1-4. The efficiency retention rates of each device after storage in a nitrogen glove box for 400 hours and in air at 30% relative humidity for 340 hours are shown in Table 2.

[0073] The test results show that device A prepared in Example 1 exhibits the best stability, with efficiency retention rates of 78.3% and 80.4% in nitrogen and air environments, respectively, both significantly higher than those of the comparative devices. In particular, in air, the efficiency retention rate of device B1 prepared in Comparative Example 1 without PC modifier is only 50.6%, far lower than the 80.4% of device A.

[0074] The aforementioned stability differences are mainly attributed to the dual modification effect of the PC modifier on the tin dioxide electron transport layer. On the one hand, the oxygen atoms in the PC molecule and Sn... 4+ Coordination effectively passivates interface defects and enhances the interface stability between the electron transport layer and the perovskite light absorption layer. On the other hand, its conjugated structure regulates the crystallization process of perovskite, promoting the formation of larger perovskite grains with fewer grain boundaries, thereby effectively suppressing the α→δ phase transition that easily occurs in air in all-inorganic perovskite.

[0075] Table 2. Stability test results for each battery

[0076]

[0077] Figure 4 These are optical microscope images of the degradation process of the perovskite films in Example 1 (A) and Comparative Example 1 (B1) under air. The optical microscope observations further confirm that the perovskite film in device A retains its black photoactive phase for 45 minutes, while the perovskite film in device B1 changes from black to yellow within 15 minutes, exhibiting a significant phase transition.

[0078] Figure 5 Comparing the energy level structures of the perovskite light absorption layer before and after modification with potassium 3-phenyl-2-acrylate in Example 1, the conduction band bottom (CBM) and Fermi level (E_F) of the electron transport layer both shift upward after PC modification. This energy level structure evolution indicates that the present invention achieves dual beneficial effects through PC modification: First, the conduction band energy level difference between tin dioxide and the perovskite layer is reduced, significantly lowering the electron injection barrier and improving charge extraction efficiency; second, the built-in electric field is enhanced. Due to the reduction in the work function of tin dioxide, the built-in electric field of the device is strengthened, promoting effective charge separation and significantly suppressing interface recombination.

Claims

1. A method for preparing a perovskite solar cell based on modification of an electron transport layer, characterized by, From bottom to top, it includes ITO conductive substrate, doped conjugated organic acid potassium salt modified tin dioxide electron transport layer, perovskite light absorption layer and carbon electrode; the conjugated organic acid potassium salt is 3-phenyl-2-propenoic acid potassium, abbreviated as PC, the molecular formula is C9H7KO2, and the material of the perovskite light absorption layer is CsPbI2Br.

2. A method for preparing a perovskite solar cell based on modification of an electron transport layer, characterized by, The method comprises the following steps: (1) pretreating the ITO conductive substrate; (2) coating the doped conjugated organic acid potassium salt modified tin dioxide solution on the ITO conductive substrate, and annealing to obtain the modified tin dioxide electron transport layer; (3) coating the perovskite precursor solution on the modified electron transport layer, and performing two-step annealing to obtain the perovskite light absorption layer; (4) uniformly coating the carbon paste on the perovskite light absorption layer to prepare the carbon electrode. 3.The method for preparing a perovskite solar cell based on an electron transport layer modification according to claim 1 or 2, characterized in that, In step (1), the ITO conductive substrate needs to be sequentially cleaned by glass cleaning agent, deionized water, isopropanol and ethanol before use, and then dried and subjected to ozone treatment. 4.The method for preparing a perovskite solar cell based on an electron transport layer modification according to claim 1 or 2, characterized in that, In step (2), the preparation method of the modified tin dioxide solution is solution doping, that is, different concentrations of 3-phenyl-2-propenoic acid potassium salt solution are added dropwise into the diluted tin dioxide solution, and then mixed uniformly to obtain the modified tin dioxide precursor solution. 5.The method for preparing a perovskite solar cell based on an electron transport layer modification according to claim 1 or 2, characterized in that, In step (2), the 3-phenyl-2-propenoic acid potassium salt solution and the tin dioxide aqueous solution are mixed in proportion to obtain a modified tin dioxide solution with a concentration of 0.05 mg / ml to 0.25 mg / ml, and after preparation, the solution is left to stand for 12 h to 24 h to ensure complete dissolution; the tin dioxide nanoparticle dispersion liquid can be selected from the market as required, and the concentration is 2 wt% to 4 wt%, which can be diluted with deionized water to obtain the required tin dioxide solution. 6.The method for preparing a perovskite solar cell based on an electron transport layer modification according to claim 1 or 2, characterized in that, In step (2), the coating amount is 40 μL to 60 μL; the coating method is spin coating, the modified tin dioxide precursor solution is added dropwise on the ITO conductive substrate, and spin coating is performed at a speed of 3000 rpm for 30 s; the annealing is performed at 150 ℃ for 15 min to 30 min; and the ozone treatment is performed for 15 min to 20 min.

7. The method for preparing a perovskite solar cell based on electron transport layer modification according to claim 1 or 2, characterized in that, In step (3), the CsPbI2Br perovskite precursor solution is prepared by dissolving cesium iodide, lead iodide and lead bromide in a mixed solvent of dimethyl sulfoxide and N,N-dimethylformamide, and then left to stand for 12 h to 24 h. 8.The method for preparing a perovskite solar cell based on an electron transport layer modification according to claim 1 or 2, characterized in that, In step (3), the coating is two-step spin coating, first spin coating at 1000 rpm for 10 s, and then spin coating at 3000 rpm for 30 s; 10 s to 20 s before the end of spin coating, a hot air flow perpendicular to the substrate is applied at a distance of 5 cm to 10 cm above the substrate. 9.The method for preparing a perovskite solar cell based on an electron transport layer modification according to claim 1 or 2, characterized in that, In step (3), the two-step annealing comprises: first low-temperature annealing at 120 ℃ for 30 s, and then high-temperature annealing at 250 ℃ to 275 ℃ for 10 min. 10.The method for preparing a perovskite solar cell based on an electron transport layer modification according to claim 1 or 2, characterized in that, In step (4), the doctor blade coating process is performed after covering a special-shaped mask plate on the light absorption layer, and the thickness of the carbon electrode is controlled to be 45 μm to 50 μm; the annealing operation is performed at 120 ℃ for 20 min.

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