Surpassing 90% Shockley–Queisser VOC limit in 1.79 eV wide-bandgap perovskite solar cells using bromine-substituted self-assembled monolayers

• Published in: Energy & environmental science Vol. 18; no. 4; pp. 1847 - 1855
• Main Authors: Zhouyin Wei, Zhou, Qilin, Niu, Xiuxiu, Liu, Shunchang, Dong, Zijing, Liang, Haoming, Chen, Jinxi, Shi, Zhuojie, Wang, Xi, Jia, Zhenrong, Guo, Xiao, Guo, Renjun, Meng, Xin, Yu-Duan, Wang, Li, Nengxu, Xu, Zhiguang, Li, Zaifang, Aberle, Armin Gerhard, Yin, Xinxing, Hou, Yi
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 18.02.2025
• Subjects: Bromine; Electron-ion recombination; Energy conversion efficiency; Energy gap; Energy levels; Lead; Monolayers; Open circuit voltage; Perovskites; Phosphonic acids; Photovoltaic cells; Radiative recombination; Self-assembled monolayers; Self-assembly; Solar cells
• DOI: 10.1039/d4ee04029e
• ISSN: 1754-5692

All-perovskite tandem solar cells (TSCs) hold the promise of surpassing the efficiency limits of single-junction solar cells. However, enhancing TSC efficiency faces the challenge of significant open-circuit voltage (VOC) loss in the wide-bandgap (WBG) subcell. In this study, we employed a bromine-substitution strategy to develop a novel self-assembled monolayer, (4-(3,11-dibromo-7H-dibenzo[c,g]carbazol-7-yl)butyl)phosphonic acid (DCB-Br-2), as the hole-transporting layer for 1.79-eV WBG perovskite solar cells. The bromine in DCB-Br-2 donates a pair of non-bonded electrons to uncoordinated Pb2+ ions or halide vacancies, enhancing interaction with the perovskite layer and suppressing interfacial non-radiative recombination. DCB-Br-2 also adjusts energy level alignment, facilitating fast hole extraction. The optimized WBG solar cell achieved a maximum VOC of 1.37 V, surpassing 90% of the Shockley–Queisser limit. Combined with a 1.25-eV narrow-bandgap subcell, this enabled a two-terminal all-perovskite TSC with a champion power conversion efficiency of 27.70%, advancing the development of high-performance tandem devices.