Deciphering the Roles of MA-Based Volatile Additives for α-FAPbI3 to Enable Efficient Inverted Perovskite Solar Cells

Leyu Bi; Qiang Fu; Zixin Zeng; Yunfan Wang; Francis R Lin; Yuanhang Cheng; Hin-Lap Yip; Sai Wing Tsang; Alex K-Y Jen

doi:10.1021/jacs.2c13566

Deciphering the Roles of MA-Based Volatile Additives for α-FAPbI₃ to Enable Efficient Inverted Perovskite Solar Cells

J Am Chem Soc. 2023 Mar 15;145(10):5920-5929. doi: 10.1021/jacs.2c13566. Epub 2023 Mar 6.

Authors

Leyu Bi^{1

2

3}, Qiang Fu^{1

2

3}, Zixin Zeng¹, Yunfan Wang¹, Francis R Lin^{1

2

3}, Yuanhang Cheng⁴, Hin-Lap Yip^{1

2

3}, Sai Wing Tsang¹, Alex K-Y Jen^{1

2

3}

Affiliations

¹ Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, P. R. China.
² Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong 999077, P. R. China.
³ Hong Kong Institute for Clean Energy, City University of Hong Kong, Kowloon, Hong Kong 999077, P. R. China.
⁴ School of New Energy, Nanjing University of Science and Technology, Nanjing 214443, Jiangsu, P. R. China.

PMID: 36877962
DOI: 10.1021/jacs.2c13566

Abstract

Functional additives that can interact with the perovskite precursors to form the intermediate phase have been proven essential in obtaining uniform and stable α-FAPbI₃ films. Among them, Cl-based volatile additives are the most prevalent in the literature. However, their exact role is still unclear, especially in inverted perovskite solar cells (PSCs). In this work, we have systematically studied the functions of Cl-based volatile additives and MA-based additives in formamidinium lead iodide (FAPbI₃)-based inverted PSCs. Using in situ photoluminescence, we provide clear evidence to unravel the different roles of volatile additives (NH₄Cl, FACl, and MACl) and MA-based additives (MACl, MABr, and MAI) in the nucleation, crystallization, and phase transition of FAPbI₃. Three different kinds of crystallization routes are proposed based on the above additives. The non-MA volatile additives (NH₄Cl and FACl) were found to promote crystallization and lower the phase-transition temperatures. The MA-based additives could quickly induce MA-rich nuclei to form pure α-phase FAPbI₃ and dramatically reduce phase-transition temperatures. Furthermore, volatile MACl provides a unique effect on promoting the growth of secondary crystallization during annealing. The optimized solar cells with MACl can achieve an efficiency of 23.1%, which is the highest in inverted FAPbI₃-based PSCs.