Solar cell based on perovskite film capable of inhibiting lead leakage and preparation method thereof

Abstract

The application belongs to the technical field of semiconductor devices, and discloses a solar cell based on a perovskite film capable of inhibiting lead leakage and a preparation method thereof. A small molecule 3-MBA is used as a bifunctional Lewis base additive to be introduced into a perovskite precursor solution to prepare a perovskite film capable of inhibiting lead leakage and a solar cell. 2+ The sulfur atom of the thiol group and the oxygen atom of the carbonyl group in the 3-MBA provide two sites Pb 2 Passivation significantly improves the bonding strength and adhesion of lead in the perovskite structure, inhibits lead leakage of the perovskite solar cell, and enhances the stability of the device. In addition, due to the strong interaction between 3-MBA and the self-assembled monolayer, the influence on the device efficiency is small while inhibiting lead leakage. Experimental results show that the efficiency of a solar cell with an active area of 1cm 2 can reach 24.1%, and can present an environmental stability of more than 1900 hours at a temperature of 22 degrees and a humidity of 45%.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology and relates to the improvement of the performance of perovskite solar cell (PSC) materials and devices, specifically to solar cells based on perovskite thin films that can suppress lead leakage and their preparation methods. Background Technology

[0002] High-efficiency perovskite solar cells fabricated in existing technologies generally contain toxic lead, and the potential risk of lead leakage poses a threat to the environment and human health. Lead sequestration efficiency (SQE) is an indicator describing the effectiveness of suppressing lead leakage, and is calculated by the formula: SQE = 1 - (Lead leakage from the original perovskite / Lead leakage from the immobilized perovskite) × 100%.

[0003] One solution is to use lead-free elements. However, current lead-free perovskite solar cells either suffer from poor stability, such as tin-based perovskite cells, or have conversion efficiencies far lower than lead-based perovskite cells, such as dual perovskite solar cells. Therefore, finding methods to suppress lead leakage is a more practical solution.

[0004] Passivating perovskite films with small-molecule materials can effectively suppress lead leakage by forming bonds with free lead through Lewis base groups. However, the suppression ability of existing small-molecule materials is relatively weak. In addition, the concentration range of passivating agents is very narrow, usually from zero to a few milligrams, requiring very precise control, which is not conducive to experimental operation and industrialization.

[0005] Furthermore, the open-circuit voltage of perovskite photovoltaic cells originates from the splitting of the quasi-Fermi level between holes and electrons. When the nonradiative recombination process provides an outlet for the recombination of excess free charge carriers, it reduces the steady-state charge density, thereby decreasing the splitting of the quasi-Fermi level and ultimately lowering the open-circuit voltage. As a typical deep-level defect, uncoordinated Pb... 2+ The most serious defect on the surface of perovskite thin films is uncoordinated Pb. 2 + can capture electrons or holes, eventually leading to nonradiative recombination through the annihilation of opposite charge carriers, resulting in severe charge carrier loss and voltage deficit. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a solar cell based on a lead-leaking perovskite thin film and its preparation method. It utilizes a small-molecule 3-mercaptobenzoic acid (3-MBA) passivating agent as a bifunctional Lewis base additive for lead halide perovskites, providing dual-site Pb through the sulfur atom in the thiol group and the oxygen atom in the carbonyl group. 2+ Passivation enhances the bonding strength and adhesion of lead in the perovskite structure, suppresses lead leakage, and improves device stability.

[0007] The perovskite film that can suppress lead leakage is a lead-based perovskite film passivated with small molecules of 3-mercaptobenzoic acid (3-MBA). The composition of the perovskite film is Cs. 0.05 (FA 0.87 MA 0.13 ) 0.95 Pb(I 0.9 Br 0.1 3.

[0008] The solar cell based on a lead-leaking-suppressing perovskite thin film is an inverted perovskite solar cell structure. From bottom to top, it consists of a substrate, a self-assembled monolayer (SAM), a perovskite layer, an electron transport layer (PCBM), a hole blocking layer (BCP), and a metal back electrode. The perovskite layer is a perovskite thin film passivated with 3-mercaptobenzoic acid. The composition of the perovskite thin film is Cs. 0.05 (FA 0.87 MA 0.13 ) 0.95 Pb(I 0.9 Br 0.1 3. The electron transport layer PCBM is methyl [6,6]-phenyl C61 butyrate. The hole blocking layer PCB is copper idine.

[0009] A method for fabricating solar cells based on perovskite thin films that can suppress lead leakage is used to prepare inverted perovskite solar cells using a solution spin-coating method, specifically including the following steps:

[0010] Step 1: Perform ultrasonic cleaning on the etched substrate, and then place it in an oven to dry the surface solution.

[0011] Step 2: Prepare a 1 mg / mL MPA-CPA ethanol solution, then spin-coat it onto the dried substrate surface at 3000 rpm for 30 seconds, and then anneal it at 100 °C for 10 minutes to obtain an ultrathin self-assembled monomolecular SAM layer.

[0012] Step 3: Prepare a perovskite precursor solution and add 3-MBA small molecules at a concentration of 1–20 mg / ml. After thorough mixing, spin-coat the solution onto the surface of a self-assembled monomolecular SAM layer. Rinse with an antisolvent and then heat to obtain a passivated perovskite layer.

[0013] Step 4: Sequentially deposit an electron transport layer (PCBM), a hole blocking layer (BCP), and a metal back electrode on the surface of the passivated perovskite layer.

[0014] Preferably, the concentration of IPA dissolved in it is 1 mg / mL. -1 The PEAI solution was deposited on the perovskite film at 3000 rpm for 30 seconds as an upper surface modification layer.

[0015] Preferably, the PCBM solution is spin-coated at 1500 rpm for 30 seconds. The BCP solution is then spin-coated at 5000 rpm.

[0016] Preferably, an electrode is deposited on the surface of the hole blocking layer BCP using a vapor deposition method. The electrode is a silver electrode, a copper electrode, or a gold electrode.

[0017] The present invention has the following beneficial effects:

[0018] The sulfur atom in the thiol group and the oxygen atom in the carbonyl group of 1,3-MBA provide two Pb sites. 2+ Passivation significantly improves the bonding strength and adhesion of lead in the perovskite structure. Compared with the Pb-I and ammonium-iodine bonds in perovskites, the formed Pb-S bonds are stronger, thus contributing to improved ability to suppress lead leakage from PSCs.

[0019] 2. Due to the strong interaction between 3-MBA and the self-assembled monolayer SAM, as the concentration increases, 3-MBA molecules accumulate at the bottom of the perovskite crystal rather than directly entering the perovskite lattice. Therefore, the ability to suppress lead leakage can be improved by increasing the concentration of the additive, while having a relatively small impact on device efficiency. In addition to suppressing lead leakage, it can enhance device stability and significantly improve the open-circuit voltage and short-circuit density of the device by passivating deep-level defects in the perovskite, thereby improving the device conversion efficiency.

[0020] 3. The passivating agent 3-MBA selected in this application is not sensitive to concentration, and the selectable concentration range is 1 to 20 mg / mL. Compared with the small molecule passivating agents used in the prior art, its concentration control range is expanded by tens or even hundreds of times. The larger concentration control range is beneficial to experimental operation and industrial application.

[0021] 4. Experiments show that the perovskite solar cells prepared using perovskite thin films modified with 3-MBA passivator have an efficiency of up to 24.1% when the activated area is 1 square centimeter, and exhibit excellent device environmental stability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of an inverted perovskite solar cell structure.

[0023] Figure 2 A scanning electron microscope image of the perovskite layer prepared in Comparative Example 1;

[0024] Figure 3 The JV curve is shown for the perovskite solar cell prepared in Comparative Example 1.

[0025] Figure 4 A scanning electron microscope image of the perovskite layer prepared in Example 1;

[0026] Figure 5 This is a scanning electron microscope image of the perovskite layer prepared in Example 2;

[0027] Figure 6 The results show the lead concentration and lead storage efficiency of the perovskite solar cells prepared in Comparative Example 1 and Examples 1-2.

[0028] Figure 7 The JV curve is shown for the perovskite solar cell prepared in Example 2.

[0029] Figure 8 The results show the stability test results of the perovskite solar cells prepared in Comparative Example 1 and Examples 1-2. Detailed Implementation

[0030] This application proposes a solar cell based on a lead-leaking perovskite thin film and its preparation method. A small-molecule 3-mercaptobenzoic acid (3-MBA) passivating agent is introduced into the perovskite precursor as a bifunctional Lewis base additive to passivate uncoordinated Pb. 2 +Defects, while suppressing lead leakage in inverted perovskite solar cells. The invention will be further explained below with reference to the accompanying drawings and comparative examples;

[0031] Comparative Example 1

[0032] This comparative example prepares a such... Figure 1 The conventional inverted perovskite solar cell shown is used as a control group for performance testing. The specific steps are as follows:

[0033] Step 1: Use detergent, deionized water, isopropanol and ethanol in sequence to ultrasonically clean the etched ITO for 20 minutes, and then put it in an oven to dry the surface solution.

[0034] Step 2: Dissolve 1 mg of MPA-CPA in 1 mL of ethanol to prepare SAM solution.

[0035] Step 3: Spin-coat the SAM solution onto the dried ITO surface at 3000 rpm for 30 seconds, and then anneal at 100°C for 10 minutes to obtain an ultrathin SAM layer.

[0036] Step 4: Weigh 18.2 mg of CsI, 190.2 mg of FAI, 35.6 mg of MAI, 548.4 mg of PbI2 and 77.1 mg of PbBr2, and dissolve them in a mixed solution of 800 μL of DMF and 200 μL of DMSO to prepare a perovskite precursor solution.

[0037] Step 5: Spin-coat the perovskite precursor solution onto the surface of the ultrathin SAM layer in two stages. Set up a spin coater to spin coat at 1000 rpm for 10 s in the first stage and at 3000 rpm for 30 s in the second stage. Add 150 μL of chlorobenzene in the last 5 s of the second stage spin coating. After annealing, the perovskite layer is formed.

[0038] The surface morphology of the perovskite layer was observed using scanning electron microscopy (SEM), such as... Figure 2 As shown.

[0039] Step 6: Dissolve the IPA in water to a concentration of 1 mg / mL. -1 The PEAI solution was deposited on the perovskite film at 3000 rpm for 30 seconds to obtain an upper interface modification layer with a thickness of 1 nm. Then, a PCBM solution (20 mg / mL of CB) was spin-coated at 1500 rpm. -1 30 seconds. Spin coat with BCP solution (0.5 mg / mL of IPA) at 5000 rpm. -1) .

[0040] Step 7: Using vapor deposition, a 100 nm thick silver electrode is deposited on the BCP surface to obtain a conventional inverted perovskite solar cell. The efficiency of the fabricated inverted perovskite solar cell is detected using a solar simulator, and the JV curve is shown below. Figure 3 As shown, the effective activation area of ​​the inverted perovskite solar cell is 1 cm². 2 The reverse scan efficiency is 22.5%. The open-circuit voltage is 1.15V, and the short-circuit density is 23.5mA / cm². 2 .

[0041] Example 1

[0042] In this embodiment, 1 mg of 3-MBA small molecules were dissolved in 1 ml of perovskite precursor solution for passivation treatment of the perovskite thin film during the preparation of inverted perovskite solar cells. The specific steps are as follows:

[0043] Step 1: Use detergent, deionized water, isopropanol and ethanol in sequence to ultrasonically clean the etched ITO for 20 minutes, and then put it in an oven to dry the surface solution.

[0044] Step 2: Dissolve 1 mg of MPA-CPA in 1 mL of ethanol to prepare SAM solution.

[0045] Step 3: Spin-coat the SAM solution onto the dried ITO surface at 3000 rpm for 30 seconds, and then anneal at 100°C for 10 minutes to obtain an ultrathin SAM layer.

[0046] Step 4: Weigh 1 mg of 3-MBA small molecule, 18.2 mg of CsI, 190.2 mg of FAI, 35.6 mg of MAI, 548.4 mg of PbI2 and 77.1 mg of PbBr2, and dissolve them in a mixed solution of 800 μL of DMF and 200 μL of DMSO to prepare a perovskite precursor solution.

[0047] Step 5: Spin-coat the perovskite precursor solution onto the surface of the ultrathin SAM layer in two stages. Set up a spin coater to spin coat at 1000 rpm for 10 s in the first stage and at 3000 rpm for 30 s in the second stage. Add 150 μL of chlorobenzene in the last 5 s of the second stage spin coating. Anneal at 100°C for 20 minutes to form the passivated perovskite layer.

[0048] The surface morphology of the passivated perovskite layer was observed using scanning electron microscopy (SEM), such as... Figure 4 As shown.

[0049] Step 6: Dissolve the IPA in water to a concentration of 1 mg / mL. -1 The PEAI solution was deposited on the perovskite film at 3000 rpm for 30 seconds to obtain an upper interface modification layer with a thickness of 1 nm. Then, a PCBM solution (20 mg / mL of CB) was spin-coated at 1500 rpm. -1 30 seconds. Spin coat with BCP solution (0.5 mg / mL of IPA) at 5000 rpm. -1) .

[0050] Step 7: Using vapor deposition, a silver electrode with a thickness of 100 nm is deposited on the BCP surface to obtain a conventional inverted perovskite solar cell.

[0051] Example 2

[0052] In this embodiment, based on Example 1, 10 mg of 3-MBA small molecules were dissolved in 1 ml of perovskite precursor solution for passivation treatment of the perovskite thin film during the fabrication of an inverted perovskite solar cell. The surface morphology of the passivated perovskite layer was observed using scanning electron microscopy (SEM). Figure 5 As shown.

[0053] The lead concentration and lead storage efficiency of the perovskite solar cells prepared in Comparative Example 1, Example 1, and Example 2 were tested, and the results are as follows: Figure 6 As shown, the lead containment efficiency in Comparative Example 1 is 0, meaning that all lead will leak out. In contrast, the lead containment efficiencies in Examples 1 and 2 are 29% and 62%, respectively, indicating that passivation treatment with 3-MBA small molecule solution significantly reduces lead leakage.

[0054] Figure 7 The JV curve of the perovskite solar cell prepared in Example 2 shows an effective activated area of ​​1 cm² and a reverse scan efficiency of approximately 24.1%. It can be seen that compared to the perovskite solar cell prepared in Comparative Example 1, the conversion efficiency of Example 2 is significantly improved, with the open-circuit voltage increasing from 1.15 V to 1.17 V and the short-circuit current density reaching 24.4 mA / cm². 2 .

[0055] Figure 8 The results of stability tests on the perovskite solar cells prepared in Comparative Example 1, Example 1, and Example 2 at a temperature of 22 degrees Celsius and a humidity of 45% show that, over a period of more than 1900 hours, the perovskite solar cells prepared in the examples exhibit significantly greater stability compared to the perovskite solar cells prepared in Comparative Example 1.

[0056] Example 3

[0057] Based on Example 2, this embodiment dissolves 15, 18, and 20 mg of 3-MBA small molecules in 1 ml of perovskite precursor solution to prepare three inverted perovskite solar cells with different passivation degrees. The efficiency was measured, and it was found that when the concentration of 3-MBA small molecules was in the range of 10–20 mg / mL, the efficiency of the prepared inverted perovskite solar cells remained essentially unchanged. When the concentration of 3-MBA small molecules reached 20 mg / mL, the efficiency began to decrease. Therefore, the selectable concentration range for using 3-MBA small molecules as a passivating agent is 1–20 mg / mL.

Claims

1. A perovskite thin film capable of suppressing lead leakage, characterized in that: The perovskite film is a lead-based perovskite film passivated by adding small molecules of 3-mercaptobenzoic acid to a perovskite precursor solution; the composition of the perovskite film is Cs. 0.05 (FA 0.87 MA 0.13 ) 0.95 Pb(I 0.9 Br 0.1 3.

2. A solar cell based on a perovskite thin film capable of suppressing lead leakage, characterized in that: The perovskite layer of the solar cell is the perovskite thin film as described in claim 1.

3. The solar cell based on a lead-leaking perovskite thin film as described in claim 2, characterized in that: The solar cell is an inverted perovskite solar cell structure, consisting of, from bottom to top, a substrate, a self-assembled monolayer, a perovskite layer, an electron transport layer, a hole blocking layer, and a metal back electrode.

4. The solar cell based on a lead-leaking perovskite thin film as described in claim 2, characterized in that: An upper interface modification layer is provided between the perovskite layer and the electron transport layer of the solar cell.

5. The method for preparing a solar cell based on a lead-leaking perovskite thin film as described in claim 2, characterized in that: Prepared using a solution spin coating method, 3-MBA small molecules are added to a perovskite precursor solution, wherein the concentration of the 3-MBA small molecules is 1~20 mg / ml.

6. The method for preparing a solar cell based on a lead-leaking perovskite thin film as described in claim 5, characterized in that: The concentration of the 3-MBA small molecule is 1~10 mg / ml.

7. The method for preparing a solar cell based on a lead-leaking perovskite thin film as described in claim 5, characterized in that: Specifically, the following steps are included: Step 1: Perform ultrasonic cleaning on the etched substrate, and then place it in an oven to dry the surface solution; Step 2: Prepare a 1 mg / mL MPA-CPA ethanol solution, spin-coat it onto the dried substrate surface, and anneal it to obtain an ultrathin self-assembled monomolecular SAM layer; Step 3: Prepare the perovskite precursor solution and add 3-MBA small molecules; After thorough mixing, the mixture was spin-coated onto the surface of a self-assembled monomolecular SAM layer. After rinsing with an antisolvent and heating, a passivated perovskite layer was obtained. Step 4: Sequentially deposit an electron transport layer, a hole blocking layer, and a metal back electrode on the surface of the passivated perovskite layer to obtain a solar cell.

8. The method for preparing a solar cell based on a lead-leaking perovskite thin film as described in claim 7, characterized in that: A PEAI solution with a concentration of 1 mg / mL dissolved in IPA was deposited on the surface of the passivated perovskite layer at 3000 rpm for 30 seconds as the upper surface modification layer. The application of 9,3-mercaptobenzoic acid small molecules in the preparation of perovskite thin films, characterized by: The 3-mercaptobenzoic acid small molecule was added to the perovskite precursor solution to passivate the perovskite film. The composition of the perovskite film was Cs. 0.05 (FA 0.87 MA 0.13 ) 0.95 Pb(I 0.9 Br 0.1 3.

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