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

Abstract

The invention belongs to the technical field of semiconductor devices, and discloses a solar cell based on a perovskite thin film capable of inhibiting lead leakage and a preparation method of the solar cell. 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 thin film and a solar cell capable of inhibiting lead leakage. According to the invention, sulfur atoms of thiol groups and oxygen atoms of carbonyl groups in 3-MBA are utilized to provide double-site Pb < 2 + > passivation, so that the bonding strength and adhesive force of lead in a perovskite structure are remarkably improved, lead leakage of the perovskite solar cell is inhibited, and the stability of a device is enhanced. Besides, due to the strong interaction between the 3-MBA and the self-assembly monomolecular layer, the influence on the efficiency of the device is small while the lead leakage is inhibited, and experiments prove that the efficiency of the solar cell with the activated area of 1cm < 2 > can reach 24.1%, and the solar cell can show the environmental stability of more than 1900 hours at the temperature of 22 DEG C and the humidity of 45%.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and relates to the improvement of perovskite solar cell (PSCs) materials and device performance. Specifically, it relates to a solar cell based on a perovskite thin film capable of suppressing lead leakage and a preparation method thereof. Background Art

[0002] In the high-efficiency perovskite cells prepared in the prior art, toxic lead elements are generally contained, and the potential risk of lead leakage poses a threat to the environment and human health. The lead-sealing efficiency (SQE) is an index describing the effect of suppressing lead leakage, and the calculation formula is SQE = 1 - (lead leaked from the original perovskite / lead leaked from the fixed perovskite) × 100%.

[0003] One solution is to use lead-free elements. However, current lead-free perovskite cells either have poor stability, such as tin-based perovskite cells, or have a conversion efficiency much lower than that of lead-based perovskite cells, such as double perovskite solar cells. Therefore, finding a method to suppress lead leakage is a more practical solution.

[0004] Passivating the perovskite thin film with small molecule materials can effectively suppress lead leakage by forming binding bonds between the Lewis base groups and free lead. However, the existing small molecule materials have weak inhibitory ability. In addition, the concentration range of the passivator is very narrow, usually from zero to a few milligrams, and very fine or precise control is required, which is not conducive to experimental operation and industrialization.

[0005] In addition, the open-circuit voltage of perovskite photovoltaic cells comes from the splitting of the quasi-Fermi levels of holes and electrons. When the non-radiative recombination process provides an outlet for the recombination of excess free charge carriers, it reduces the steady-state charge density, thereby reducing the splitting of the quasi-Fermi levels and ultimately reducing the open-circuit voltage. As a typical deep-level defect, uncoordinated Pb 2+ is the most serious defect on the surface of the perovskite thin film. Uncoordinated Pb 2+ can capture electrons or holes, and ultimately cause non-radiative recombination through the annihilation of opposite charge carriers, resulting in serious charge carrier loss and voltage deficit. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention proposes a solar cell based on a perovskite thin film capable of suppressing lead leakage and a preparation method thereof. Using a small molecule 3-mercaptobenzoic acid (3-MBA) passivator as a bifunctional Lewis base additive for lead halide perovskite, it provides double sites Pb 2+ for passivation through the sulfur atom in the mercapto group and the oxygen atom in the carbonyl group, improves the binding strength and adhesion of lead in the perovskite structure, the ability to suppress lead leakage, and enhances the stability of the device.

[0007] The perovskite film capable of inhibiting lead leakage is a lead-based perovskite film passivated by a small molecule of 3-mercaptobenzoic acid (3-MBA). The components of the perovskite film are 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 the perovskite film that can inhibit lead leakage is an inverted perovskite solar cell structure, which includes 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 from bottom to top. The perovskite layer is a perovskite film passivated by a small molecule of 3-mercaptobenzoic acid, and the component of the perovskite 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 [6,6]-phenyl C61 butyric acid methyl ester. The hole blocking layer PCB is bath copper pyridine.

[0009] A method for preparing a solar cell based on a perovskite film capable of inhibiting lead leakage is used to prepare an inverted perovskite solar cell using a solution spin coating method, which specifically includes the following steps:

[0010] Step 1: ultrasonically clean the etched substrate and then put it into an oven to dry the surface solution.

[0011] Step 2: Prepare a 1 mg / mL MPA-CPA ethanol solution, then spin-coat it on the dried substrate surface at a speed of 3000 rpm for 30 seconds, and then anneal 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, the concentration of which is 1-20 mg / ml. After fully mixing, spin-coat the solution on the surface of the self-assembled monolayer SAM layer, rinse with an anti-solvent and heat to obtain a passivated perovskite layer.

[0013] Step 4: depositing an electron transport layer PCBM, a hole blocking layer BCP and a metal back electrode in sequence on the surface of the perovskite layer after passivation treatment.

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

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

[0016] Preferably, the vapor deposition method is used to deposit an electrode on the surface of the hole blocking layer BCP, and the electrode is a silver electrode, a copper electrode or a gold electrode.

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

[0018] 1. The sulfur atom in the thiol group of 3-MBA and the oxygen atom in the carbonyl group provide double-site Pb 2+ passivation, significantly improving the binding strength and adhesion of lead in the perovskite structure. Compared with the Pb-I and ammonium-iodine bonds in perovskite, the formed Pb-S bond is stronger, thus contributing to improving the ability to inhibit lead leakage in PSCs.

[0019] 2. Due to the strong interaction between 3-MBA and the self-assembled monolayer SAM, as the concentration increases, 3-MBA molecules will accumulate at the bottom of the perovskite rather than directly enter the perovskite lattice. Therefore, the ability to inhibit lead leakage can be improved by increasing the concentration of the additive, and the impact on the device efficiency is relatively small. While inhibiting lead leakage, the stability of the device can be enhanced, and the open-circuit voltage and short-circuit current density of the device can be significantly improved by passivating the deep-level defects of the perovskite, thereby improving the device conversion efficiency.

[0020] 3. The selected passivating agent 3-MBA small molecule of this application is insensitive to concentration, and the selectable concentration range is 1-20 mg / mL. Compared with the small molecule passivating agents used in the prior art, its concentration regulation range has been expanded by dozens of times, or even hundreds of times, and the larger concentration regulation range is beneficial to experimental operation and industrial application.

[0021] 4. Experiments have proved that the perovskite solar cells prepared using the perovskite film modified with the 3-MBA passivating agent have an efficiency as high as 24.1% when the activation area is 1 square centimeter, and exhibit excellent device environmental stability. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the structure of a reverse perovskite solar cell;

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

[0024] Figure 3 It is a J-V curve diagram of the perovskite solar cell prepared in Comparative Example 1;

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

[0026] Figure 5 Scanning electron microscope image of the perovskite layer prepared in Example 2;

[0027] Figure 6 Lead concentration and lead encapsulation efficiency results of the perovskite solar cells prepared in Comparative Example 1 and Examples 1-2;

[0028] Figure 7 J-V curve of the perovskite solar cell prepared in Example 2;

[0029] Figure 8 Stability test results of the perovskite solar cells prepared in Comparative Example 1 and Examples 1-2; Detailed implementation mode

[0030] This application proposes a solar cell based on a perovskite thin film that can inhibit lead leakage and its preparation method. A small molecule 3-mercaptobenzoic acid (3-MBA) passivator is used and introduced into the perovskite precursor as a bifunctional Lewis base additive to passivate the uncoordinated Pb 2+ defects and simultaneously inhibit lead leakage in inverted perovskite solar cells. The present invention will be further explained and illustrated below in conjunction with the accompanying drawings and comparative examples;

[0031] Comparative Example 1

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

[0033] Step 1: Ultrasonically clean the etched ITO with detergent, deionized water, isopropanol, and ethanol in sequence for 20 minutes, and then place 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 a SAM solution.

[0035] Step 3: Spin-coat the SAM solution on the dried ITO surface at a speed of 3000 rpm for 30 seconds, and then anneal it 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 on the surface of the ultrathin SAM layer in two stages. Set the spin coater to spin at 1000 rpm for 10 s in the first stage and 3000 rpm for 30 s in the second stage. During the last 5 s of the second-stage spin-coating, add 150 μL of chlorobenzene, and then form a perovskite layer after annealing treatment.

[0038] Use a scanning electron microscope (SEM) to observe the surface morphology of the perovskite layer, as Figure 2 shown.

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

[0040] Step 7: Use the evaporation method to deposit a silver electrode with a thickness of 100 nm on the BCP surface to obtain a conventional inverted perovskite solar cell. Use a solar simulator to detect the efficiency of the prepared inverted perovskite solar cell. The J-V curve is as Figure 3 shown. The effective activation area of the inverted perovskite solar cell is 1 cm 2 , and the reverse scan efficiency is 22.5%. Among them, the open-circuit voltage is 1.15 V, and the short-circuit current density is 23.5 mA / cm 2 .

[0041] Example 1

[0042] In this example, 1 mg of 3-MBA small molecule is dissolved in 1 mL of perovskite precursor solution for passivating the perovskite film during the preparation of the inverted perovskite solar cell. The specific steps are as follows:

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

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

[0045] Step 3: Spin-coat the SAM solution on the dried ITO surface at 3000 rpm for 30 s, and then anneal it 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, 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 on the surface of the ultra-thin SAM layer in two stages. Set the spin coater to spin at 1000 rpm for 10 s in the first stage and 3000 rpm for 30 s in the second stage. And add 150 μL of chlorobenzene in the last 5 s of the second stage spin-coating, and anneal at 100 °C for 20 minutes to form a passivated perovskite layer.

[0048] Use a scanning electron microscope (SEM) to observe the surface morphology of the passivated perovskite layer, as Figure 4 shown.

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

[0050] Step 7: Use the evaporation method to deposit a silver electrode with a thickness of 100 nm on the BCP surface to obtain a conventional inverted perovskite solar cell.

[0051] Example 2

[0052] Based on Example 1, in this example, weigh 10 mg of 3-MBA small molecule and dissolve it in 1 ml of perovskite precursor solution for passivating the perovskite film during the preparation of the inverted perovskite solar cell. Use a scanning electron microscope (SEM) to observe the surface morphology of the passivated perovskite layer, as Figure 5 shown.

[0053] Test the lead concentration and lead encapsulation efficiency of the perovskite solar cells prepared in Comparative Example 1, Example 1 and Example 2. The results are as Figure 6 shown. The lead encapsulation efficiency in Comparative Example 1 is 0, which means that all the lead will leak. While the lead encapsulation efficiencies of Example 1 and Example 2 are 29% and 62% respectively, indicating that after passivation treatment with 3-MBA small molecule solution, the lead leakage will be significantly reduced.

[0054] Figure 7 J-V curve of the perovskite solar cell prepared in Example 2, with an effective activation area of 1 cm2 and a reverse scan efficiency of about 24.1%. It can be seen that compared with the perovskite solar cell prepared in Comparative Example 1, the conversion efficiency of Example 2 has been significantly improved, the open circuit voltage has increased from 1.15 V to 1.17 V, and the short circuit current density is 24.4 mA / cm 2 .

[0055] Figure 8 Stability test results of the perovskite solar cells prepared in Comparative Example 1, Example 1, and Example 2 at a temperature of 22 degrees and a humidity of 45%. It can be seen that within a range of more than 1900 hours, the perovskite solar cells prepared in Example show significantly better stability compared to the perovskite solar cells prepared in Comparative Example 1.

[0056] Example 3

[0057] On the basis of Example 2, 15, 18, and 20 mg of 3-MBA small molecules were weighed and dissolved in 1 ml of perovskite precursor solution respectively to prepare three types of inverted perovskite solar cells with different degrees of passivation, and the efficiency was measured. 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 basically unchanged. When the concentration of 3-MBA small molecules reached 20 mg / mL, the efficiency began to decline. Therefore, the selectable concentration range of using 3-MBA small molecules as a passivating agent is 1-20 mg / mL.

Claims

1. A lead leakage-inhibiting perovskite thin film, characterized in that: The perovskite film is a lead-based perovskite film passivated by 3-mercaptobenzoic acid small molecules.

2. The lead-leakage-inhibiting perovskite film according to claim 1, wherein: 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.

3. The solar cell based on a perovskite thin film capable of suppressing lead leakage is characterized in that: The perovskite layer of the solar cell is the perovskite film described in any one of claims 1 or 2.

4. The solar cell based on the perovskite thin film capable of suppressing lead leakage as claimed in claim 3, wherein: The solar cell has a structure of a p-i-n perovskite solar cell, which includes a substrate, a self-assembled monolayer, a perovskite layer, an electron transport layer, a hole blocking layer, and a metal back electrode in sequence from bottom to top.

5. The perovskite thin film-based solar cell according to claim 3, wherein: An upper interface modification layer is provided between the perovskite layer and the electron transport layer of the solar cell.

6. The preparation method of the solar cell based on the lead-leakage-inhibitable perovskite thin film as claimed in claim 3, wherein: It is prepared by solution spin coating. 3-MBA small molecules are added to the perovskite precursor solution, and the concentration of the 3-MBA small molecules is 1 to 20 mg / ml.

7. The preparation method of the solar cell based on the lead-leakage-inhibitable perovskite thin film according to claim 6, wherein: The concentration of the 3-MBA small molecules is 1 to 10 mg / ml.

8. The preparation method of the solar cell based on the lead-leakage-inhibitable perovskite thin film according to claim 6, characterized in that: Specifically, it includes the following steps: Step 1: Ultrasonically clean 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 on the surface of the dried substrate, and anneal it to obtain an ultrathin self-assembled monolayer SAM layer. Step 3: Prepare a perovskite precursor solution and add 3-MBA small molecules. After sufficient mixing, spin coat it on the surface of the self-assembled monolayer SAM layer, rinse it with an anti-solvent and then heat it to obtain a passivated perovskite layer. Step 4: Deposit an electron transport layer, a hole blocking layer, and a metal back electrode on the surface of the passivated perovskite layer in sequence to obtain a solar cell.

9. The preparation method of the solar cell based on the perovskite film capable of suppressing lead leakage according to claim 8, wherein: 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. -1 ​ 10.3 - Application of 3 - mercaptobenzoic acid small molecule in preparing perovskite thin film, characterized in that: Add the 3-mercaptobenzoic acid small molecules to the perovskite precursor solution to passivate the perovskite film.

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