Acta Phys. -Chim. Sin. ›› 2023, Vol. 39 ›› Issue (2): 2203048.

• ARTICLE •

### Two-Step Sequential Blade-Coating Large-Area FA-Based Perovskite Thin Film via a Controlled PbI2 Microstructure

Yongtao Wen1,2, Jing Li1, Xiaofeng Gao3, Congcong Tian1, Hao Zhu3, Guomu Yu1, Xiaoli Zhang4, Hyesung Park5,*(), Fuzhi Huang1,2,*()

1. 1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China
2 Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory, Foshan 528216, Guangdong Province, China
3 International School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China
4 School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China
5 Department of Materials Science and Engineering, Graduate School of Semiconductor Materials and Devices Engineering, Perovtronics Research Center, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea
• Received:2022-03-28 Accepted:2022-04-25 Published:2022-04-29
• Contact: Hyesung Park,Fuzhi Huang E-mail:hspark@unist.ac.kr;fuzhi.huang@whut.edu.cn
• About author:Email: fuzhi.huang@whut.edu.cn (F.H.)
Email: hspark@unist.ac.kr (H.P.)
• Supported by:
the National Key Research and Development Plan(2019YFE0107200);the National Key Research and Development Plan(2017YFE0131900);the National Natural Science Foundation of China(21875178);the National Natural Science Foundation of China(52172230);the National Natural Science Foundation of China(91963209);the Fundamental Research Funds for the Central Universities(202443004);Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XDT2020-001);Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory(XHT2020-005)

Abstract:

Solar cells, which are excellent alternatives to traditional fossil fuels, can efficiently convert sunlight into electricity. The intensive development of high-performance photovoltaic materials plays an important role in environmental protection and the utilization of renewable energy. Organic–inorganic hybrid perovskite materials, with a formula of ABX3 (A = methylammonium (MA) or formamidinium (FA); B = Pb or Sn; X = Cl, I, or Br), have exhibited remarkable commercial prospects in high-performance photovoltaic devices owing to their long carrier diffusion length, excellent light absorption properties, high charge carrier mobility, and weak exciton binding energy. Recently, perovskite solar cells, fabricated using halide perovskite materials as light-absorbing layers, have achieved remarkable results; their certified power conversion efficiency has continuously improved and reached 25.7%. However, high-performance devices are usually fabricated using spin-coating methods with active areas below 0.1 cm2. Hence, long-term research goals include achieving a large-scale uniform preparation of high-quality photoactive layers. The current one-step preparation of perovskite films involves the nucleation-crystalline growth process of perovskite. Auxiliary processes, such as using an anti-solvent, are often required to increase the nucleation rate and density of the film, which is not suitable for industrial large-area preparation. Additionally, the large-area preparation of perovskite films by spin-coating will result in different film thicknesses in the center and edge regions of the film due to an uneven centrifugal force. This will cause intense carrier recombination in the thicker area of the film and weak light absorption in the thinner area, which will reduce the performance of the device. To address these problems, the development of a large-area fabrication method for high-performance perovskite light-absorbing layers is essential. In this study, a two-step sequential blade-coating strategy was developed to prepare the FA-based perovskite layer. In general, PbI2 easily forms a dense film; therefore, formamidinium iodide (FAI) cannot deeply penetrate to completely react with PbI2. The PbI2 residue is therefore detrimental to charge transportation. To fabricate the desired porous PbI2 film, tetrahydrothiophene 1-oxide (THTO) was introduced into the PbI2 precursor solution. By forming PbI2·THTO complexes, PbI2 crystallization is controlled, resulting in the formation of vertically packed PbI2 flaky crystals. These crystals provide nanochannels for easy FAI penetration. The 5 cm × 5 cm modules fabricated through this strategy achieved a high efficiency of 18.65% with excellent stability. This indicates that the two-step sequential blade-coating strategy has considerable potential for scaling up the production of perovskite solar cells.

MSC2000:

• O646