Low-concentration precursor optimization method for efficient semitransparent perovskite solar cell

Abstract

The invention discloses a low-concentration precursor optimization method for a high-efficiency semitransparent perovskite solar cell, and belongs to the technical field of semitransparent perovskite solar cells, and a solvent system adopted by a precursor solution is that 30% by volume of CB is added into a DMF / NMP mixed solvent prepared according to the volume ratio of 4: 1. According to the invention, a DMF / NMP / CB mixed solvent system is developed, and the interaction between the low-concentration precursor solution and the Me-4PACz self-assembled monomolecular layer is remarkably improved by optimizing the composition and proportion of the solvent. A traditional DMF / DMSO precursor solvent is replaced by the DMF / NMP / CB mixed solvent, so that the crystallization quality of the perovskite thin film and the contact relation between the perovskite thin film and the substrate are improved; compared with other methods, the thin perovskite film prepared by the method has lower defect density and lower pinhole rate, and a corresponding device has high efficiency and excellent visible light transmittance.

Description

Technical Field

[0001] The present invention belongs to the technical field of semi - transparent perovskite solar cells, and specifically relates to a method for optimizing low - concentration precursors for high - efficiency semi - transparent perovskite solar cells. Background Art

[0002] Semi - transparent perovskite solar cells have become ideal candidates for building - integrated photovoltaics such as photovoltaic windows due to their characteristics of both power generation and light transmission. As one of the key technical indicators of photovoltaic windows, the average photopic transmittance of semi - transparent perovskite solar cells usually needs to exceed 20% to ensure meeting the actual requirements in terms of optical transparency and aesthetics. However, while achieving a relatively high average photopic transmittance, maintaining high device efficiency and stability of the device remains a major technical challenge. To meet this requirement, it is usually necessary to carry out collaborative optimization of the device at both the electrical and optical levels. The perovskite layer usually shoulders the important task of optimizing both electrical and optical properties.

[0003] Currently, a variety of methods for preparing thin perovskite films have been developed, such as thermal evaporation and low - concentration solution treatment, etc. Compared with the thermal evaporation technology with complex equipment and high cost, preparing thin perovskite films by low - concentration (<1M) solution - based treatment is more attractive. So far, most perovskite films of semi - transparent perovskite devices are prepared by solution - based methods. However, there are still many problems in the quality of these films. Especially when the film thickness is reduced to less than 200 nm, the prepared perovskite films usually exhibit higher defect density and porosity, which not only reduces the optoelectronic performance but also significantly affects the long - term stability of the device. In addition, the compatibility of the perovskite precursor solution on different substrates is also a key challenge. The precursor solution deposition process affects many parameters such as the uniformity and crystallinity of the perovskite film, carrier transport characteristics, and device stability. Recently, carbazole - based self - assembled monolayer materials with phosphonic acid anchoring groups such as [4-(3,6 - Dimethyl - 9H - carbazol - 9 - yl)butyl]phosphonic acid (Me - 4PACz, [4-(3,6 - dimethyl - 9H - carbazol - 9 - yl)butyl]phosphonic acid) have shown excellent performance in various perovskite solar cells. Among them, due to the lower defect density and better interfacial connection matching, the corresponding devices show better carrier transport performance and smaller open - circuit voltage loss. However, similar to traditional organic polymer hole - transporting layers (HTLs) such as PTAA, due to the presence of long alkyl chains and methyl groups or (-CH), Me - 4PACz is usually non - polar and hydrophobic. This makes it more difficult for the perovskite precursor solution based on traditional highly polar N,N - dimethylformamide / dimethyl sulfoxide (DMF / DMSO) mixed solvents to form a uniform coverage on its surface.

[0004] Recently, there have been some remedies for the hydrophobicity of self-assembled monolayers in opaque devices. For example, a layer of Al2O3 nanoparticles is spin-coated on the surface of Me-4PACz, a co-assembled HTL layer is used, and a p-xylylenediphosphonic acid interface layer is introduced between the Me-4PACz and perovskite layers to optimize the interface contact. Although the device performance has been improved, the beneficial properties brought by the direct interface between the perovskite and Me-4PACz may be affected by using these methods, and similar methods still face challenges in scenarios such as semi-transparent devices that require low-concentration precursor solutions. Currently, there is no optimization strategy for low-concentration perovskite precursors applied to semi-transparent devices to improve the perovskite film and its contact with the bottom interface.

[0005] Generally speaking, existing semi-transparent perovskite solar cells usually need to make a trade-off between the photoelectric conversion efficiency and the average photopic transmittance in building-integrated photovoltaic applications. To obtain high light transmittance, a thin (<200nm) perovskite active layer is usually prepared, but there are the following key problems in the film-forming process of low-concentration precursor solutions:

[0006] 1. Poor compatibility between the ink and the bottom self-assembled monolayers (SAMs)

[0007] Especially when using hydrophobic SAM materials such as Me-4PACz, the traditional high-polarity DMF / DMSO (volume ratio 4:1) solvent system is insufficient in terms of wettability and interfacial binding energy, resulting in pinholes, uneven crystallization, and interfacial defects in the film.

[0008] 2. High difficulty in film quality control

[0009] The thin perovskite layer is more sensitive to the solvent extraction kinetics and nucleation process. The film density in the existing system is insufficient, affecting the device efficiency and stability. Summary of the Invention

[0010] In view of the above technical problems, the present invention provides an optimization method for low-concentration precursors for highly efficient semi-transparent perovskite solar cells, and develops a DMF / NMP / CB (4:1, 30% Vol chlorobenzene) mixed solvent system. By optimizing the solvent composition and ratio, the interaction between the low-concentration precursor solution and the Me-4PACz self-assembled monolayer is significantly improved. The core innovation points include:

[0011] 1. Innovation in solvent system design

[0012] Introduce NMP (N-methylpyrrolidone) solvent (high donor number and high boiling point) to delay the perovskite crystallization rate and improve the wettability and binding energy between the precursor solution and Me-4PACz.

[0013] Adjust the proportion of chlorobenzene (CB) (30%), precisely control the film crystallization rate and the solvent extraction process, and achieve uniform film deposition.

[0014] 2. Optimization of interfacial interaction mechanism

[0015] Verified by density functional theory (DFT) calculations, the interfacial binding energy between NMP and Me-4PACz is stronger, promoting the uniform spreading and crystallization of the precursor, and avoiding the formation of pinholes and grain boundary defects in the film.

[0016] 3. Method for preparing high-quality perovskite films with low-concentration precursor solutions

[0017] This system achieves high densification and low defect density for films with a thickness of <200 nm, ensures the continuity and interfacial quality of the films, and effectively improves the optoelectronic performance and long-term stability of the devices.

[0018] The object of the present invention can be achieved by the following technical solutions:

[0019] A method for optimizing low-concentration precursors for highly efficient semi-transparent perovskite solar cells. Different from the traditional precursor solution using a DMF / DMSO solvent system, the solvent system used in the precursor solution of the present invention is DMF:NMP-CB: 30% by volume of CB is added to a DMF / NMP mixed solvent prepared at a volume ratio of 4:1.

[0020] Specifically as follows:

[0021] 1) The ITO conductive glass is successively ultrasonically cleaned with glass cleaner, deionized water, acetone, and ethanol, and finally dried with nitrogen.

[0022] 2) Disperse 10 - 20 mg of nickel oxide in 1 ml of deionized water and ultrasonicate for 2 minutes for standby. Subsequently, spin-coat it on the prepared ITO conductive glass at a speed of 3000 - 5000 rpm and anneal it at 100 - 150 °C for 15 minutes to form a nickel oxide layer.

[0023] 3) Spin-coat the Me-4pacz solution (0.5 - 1 mg·mL -1 in isopropanol) on the nickel oxide layer and anneal it at 100 - 120 °C for 10 minutes to obtain an ITO / NiOx / Me-4pacz substrate.

[0024] 4) Mix MACl (methylammonium chloride), PbI2 (lead iodide), PbBr2 (lead bromide), CsI (cesium iodide), FAI (formamidinium hydroiodide), and MABr (methylammonium bromide) in a mixed solvent according to the stoichiometric ratio to prepare a 0.5 M Cs 0.05 (FA 0.95 MA 0.05 )0.95 Pb(I 0.95 Br 0.05 )3 precursor solution;

[0025] The solvent system used is DMF:NMP-CB (30% by volume of CB is added to the DMF / NMP mixed solvent prepared at a volume ratio of 4:1);

[0026] 5) Prepare the CsFAMA triple-cation perovskite thin film on the ITO / NiOx / Me-4pacz substrate by a two-step spin-coating method. Specifically, first spin at a speed of 1000 rpm for 10 seconds, then spin at a speed of 5000 rpm for 40 seconds, then extract with CB (chlorobenzene) antisolvent for 10 seconds, and then anneal the substrate at 100-120 °C for 30 minutes;

[0027] 6) Prepare the passivation layer, which is prepared by spin-coating PEAI (phenethylammonium iodide) on the perovskite layer. Specifically, first spin at a speed of 3000-4000 rpm for 30 seconds, and then spin at a speed of 4000-5000 rpm for 30 s to spin-coat the PCBM ([6,6]-phenyl-C61-butyric acid isomethyl ester) solution (15-20 mg·mL -1 ) on top of the perovskite layer, and then spin-coat BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 0.5-0.8 mg·mL -1 ) on the PCBM surface at a speed of 4000-6000 rpm for 30 s;

[0028] 7) Finally, thermally evaporate a layer of Ag thin film and a layer of MoO3 thin film.

[0029] After testing, the efficiency of the semi-transparent perovskite thin film obtained by the present invention is 14.88%, and the average transmittance in the 300-800 nm band is 31%.

[0030] Advantages of the present invention:

[0031] By replacing the traditional DMF / DMSO precursor solvent with the DMF / NMP / CB mixed solvent, the present invention improves the crystallization quality of the perovskite thin film and the contact relationship between the perovskite thin film and the substrate;

[0032] Compared with other methods, the thin perovskite thin film prepared by the present invention has a lower defect density and a lower pinhole rate, and the corresponding device has high efficiency and excellent visible light transmittance. Brief description of the drawings

[0033] The present invention will be further described below with reference to the accompanying drawings.

[0034] Figure 1SEM image of the semi-transparent perovskite thin film of Example 1.

[0035] Figure 2 XRD patterns of the semi-transparent perovskite thin films of Example 1 and Comparative Example 1.

[0036] Figure 3 Comparison chart of the stability of the semi-transparent perovskite devices of Example 1 and Comparative Example 1. Detailed implementation manners

[0037] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0038] Example 1

[0039] A method for optimizing low-concentration precursors for highly efficient semi-transparent perovskite solar cells is as follows:

[0040] 1) ITO conductive glass is successively ultrasonically cleaned with glass cleaning agent, deionized water, acetone, and ethanol, and finally dried with nitrogen.

[0041] 2) 10 - 20 mg of nickel oxide is dispersed in 1 mL of deionized water and ultrasonically treated for 2 minutes for standby. Subsequently, it is spin-coated on the prepared ITO conductive glass at a speed of 3000 - 5000 rpm and annealed at 100 - 150 °C for 15 minutes to form a nickel oxide layer.

[0042] 3) The Me-4pacz solution (0.5 - 1 mg·mL -1 in isopropanol) is spin-coated on the nickel oxide layer and annealed at 100 - 120 °C for 10 minutes to obtain an ITO / NiOx / Me-4pacz substrate.

[0043] 4) MACl, PbI2, PbBr2, CsI, FAI, and MABr are mixed in a stoichiometric ratio in a mixed solvent to prepare a 0.5 M Cs 0.05 (FA 0.95 MA 0.05 ) 0.95 Pb(I 0.95 Br 0.05 )3 precursor solution; the solvent system used is DMF:NMP-CB (30% by volume of CB is added to the DMF / NMP mixed solvent prepared at a volume ratio of 4:1).

[0044] 5) The CsFAMA triple-cation perovskite thin film was prepared on the ITO / NiOx / Me-4pacz substrate by a two-step spin-coating method. Specifically, it was first spun at a speed of 1000 rpm for 10 seconds, then spun at a speed of 5000 rpm for 40 seconds, and then extracted with a CB antisolvent for 10 seconds. Subsequently, the substrate was annealed at 100 - 120 °C for 30 minutes;

[0045] 6) A passivation layer was prepared by spin-coating PEAI on the perovskite layer. Specifically, it was first spun at a speed of 3000 - 4000 rpm for 30 seconds, and then spun at a speed of 4000 - 5000 rpm for 30 s to spin-coat the PCBM solution (15 - 20 mg·mL -1 ) on top of the perovskite layer. Then, BCP (0.5 - 0.8 mg·mL -1 ) was quickly spin-coated on the surface of the PCBM at a speed of 4000 - 6000 rpm for 30 s;

[0046] 7) Finally, a layer of Ag thin film and a layer of MoO3 thin film were thermally evaporated.

[0047] Comparative Example 1

[0048] Compared with Example 1, the solvent system used in step 4) was DMF-DMSO (4:1 / V:V), and the rest of the processes and conditions were the same.

[0049] Comparative Example 2

[0050] Compared with Example 1, the solvent system used in step 4) was DMF-NMP-CB (20% by volume of CB was added to the DMF / NMP mixed solvent prepared at a volume ratio of 4:1), and the rest of the processes and conditions were the same.

[0051] Comparative Example 3

[0052] Compared with Example 1, the solvent system used in step 4) was DMF-NMP-CB (40% by volume of CB was added to the DMF / NMP mixed solvent prepared at a volume ratio of 4:1), and the rest of the processes and conditions were the same.

[0053] As Figure 1 shown, it is the scanning electron microscope image of the semi-transparent perovskite thin film of Example 1. It can be seen that the prepared perovskite thin film is dense and pinhole-free. As Figure 2 shown, it is the X-ray diffraction test pattern of Example 1 and Comparative Example 1. It can be seen that compared with Comparative Example 1, the diffraction peaks of Example 1 show higher intensity, indicating that the perovskite thin film of Example 1 has better crystallization quality. As Figure 3As shown, it is the storage stability test chart of Example 1 and Comparative Example 1. It can be seen that compared with Comparative Example 1, the performance of the unencapsulated semi-transparent perovskite solar cell in Example 1 still remains above 90% after being stored for 1000 hours under the conditions of 25 degrees Celsius and 25% humidity.

[0054] The efficiency data and transmittance data (average value of transmittance from 400nm to 800nm) obtained for the semi-transparent perovskite cells prepared in the above Example 1 and Comparative Examples 1 to 3 are shown in the following table:

[0055]

[0056] It can be seen from the table that the semi-transparent perovskite solar cell in Example 1 has a higher open-circuit voltage and photoelectric conversion efficiency. In addition, the corresponding device has an average visible light transmittance of about 31% in the range of 400 - 800nm, demonstrating excellent light-transmitting performance.

[0057] The above specific implementation part has specifically introduced the analysis method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and idea of the present invention, rather than a limitation on the relevant content. Without departing from the principle of the present invention, those skilled in the art can also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications should also fall within the protection scope of the present invention.

Claims

1. A low-concentration precursor optimization method for efficient semi-transparent perovskite solar cells, characterized in that, The solvent system used for the precursor solution is as follows: 30% by volume of CB is added to a DMF / NMP mixed solvent prepared at a volume ratio of 4:

1.

2. The low-concentration precursor optimization method for an efficient semi-transparent perovskite solar cell according to claim 1, wherein Specifically as follows: 1) Pretreatment of ITO conductive glass; 2) Spin-coat the nickel oxide dispersion on the prepared ITO conductive glass and anneal to form a nickel oxide layer; 3) Spin-coat the Me-4pacz solution on the nickel oxide layer and anneal to obtain an ITO / NiOx / Me-4pacz substrate; 4) Mix MACl, PbI2, PbBr2, CsI, FAI, and MABr in a stoichiometric ratio in a mixed solvent to prepare a 0.5 M Cs 0.05 (FA 0.95 MA 0.05 ) 0.95 Pb(I 0.95 Br 0.05 )3 precursor solution; the solvent system used is: add 30% by volume of CB to a DMF / NMP mixed solvent prepared at a volume ratio of 4:1; 5) Prepare a CsFAMA triple-cation perovskite thin film on the ITO / NiOx / Me-4pacz substrate by a two-step spin-coating method; 6) Prepare a passivation layer by spin-coating PEAI on the perovskite layer; 7) Finally, thermally evaporate a layer of Ag film and a layer of MoO3 film.

3. The low-concentration precursor optimization method for an efficient semi-transparent perovskite solar cell according to claim 2, wherein The specific operation of step 1) is as follows: The ITO conductive glass is successively ultrasonically cleaned with a glass cleaner, deionized water, acetone, and ethanol, and finally dried with nitrogen.

4. A method for optimizing low-concentration precursors for highly efficient semi-transparent perovskite solar cells according to claim 2, characterized in that In step 2), the nickel oxide dispersion is a dispersion obtained by dispersing 10 - 20 mg of nickel oxide in 1 ml of deionized water and ultrasonically treating for 2 minutes; the spin-coating speed of the nickel oxide dispersion is 3000 - 5000 rpm; the annealing parameters are: temperature 100 - 150 °C, time 15 minutes.

5. The low-concentration precursor optimization method for an efficient semi-transparent perovskite solar cell according to claim 2, wherein In step 3), the concentration of the Me-4pacz solution is 0.5 - 1 mg·mL -1 , and the dispersion solvent is isopropanol; annealing parameters: anneal at 100 - 120 °C for 10 minutes.

6. A method for optimizing low-concentration precursors for highly efficient semi-transparent perovskite solar cells according to claim 2, characterized in that The specific operation of step 5): First, rotate at a speed of 1000 rpm for 10 seconds, then rotate at a speed of 5000 rpm for 40 seconds, then extract with a CB antisolvent for 10 seconds, and then anneal the substrate at 100 - 120 °C for 30 minutes.

7. A method for optimizing low-concentration precursors for highly efficient semi-transparent perovskite solar cells according to claim 2, characterized in that The specific operation of step 6): First, rotate at a speed of 3000 - 4000 rpm for 30 seconds, then rotate at a speed of 4000 - 5000 rpm for 30 s to spin-coat the PCBM solution on the perovskite layer, and then quickly spin-coat BCP on the surface of PCBM at a speed of 4000 - 6000 rpm for 30 s.

8. A method for optimizing low-concentration precursors for highly efficient semi-transparent perovskite solar cells according to claim 1 or 2, characterized in that The efficiency of the obtained semitransparent perovskite thin film is 14.88%, and the average transmittance in the 300 - 800 nm band is 31%.

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