Double-site defect passivation of perovskite film via fullerene additive engineering toward highly efficient and stable bulk heterojunction solar cells

• DOI: 10.1016/j.nantod.2021.101164
• Publication Date: 2021-04-28T18:46:57Z
• Authors: Lingbo Jia; Fanyang Huang; Honghe Ding; Chuang Niu; Yanbo Shang; Wanpei Hu; Xingcheng Li; Xin Yu; Xiaofen Jiang; Ruiguo Cao; Junfa Zhu; Guan-Wu Wang; Muqing Chen; Shangfeng Yang
• Keywords: Passivation; Moiety

Abstract Bulk heterojunction (BHJ) perovskite solar cells (PVKSCs) are advantageous in passivating defects and facilitating electron extraction/transport. Most of the reported fullerene derivatives involved in BHJ-PVKSCs render single-site interactions, limiting their passivation effect. Herein, we developed a perfluoroalkyl and pyridine-cofunctionalized fullerene derivative (C60-PyF15), and applied it as an additive of CH3NH3PbI3 layer to construct inverted (p-i-n) BHJ-PVKSCs, affording double-site defect passivation of perovskite film and a champion power conversion efficiency of 20.10%, which is among the highest values for fullerene-incorporated inverted BHJ-PVKSCs. To elucidate the crucial role of the perfluoroalkyl group in efficiency enhancement, another analogous novel non-fluoro-substituted pyridine-functionalized fullerene derivative with the same chain length of alkyl group (C60-PyH15) was also synthesized, which afforded a champion PCE of 19.22% and is lower than that of C60-PyF15. The double-site defect passivation ability of C60-PyF15 is resulted from the coordination interaction of the pyridine moiety with Pb2+ ions and hydrogen bonding between the fluorine atom within the perfluoroalkyl group and the CH3NH3+ cations. These enable ordered orientation of CH3NH3+ and suppressed ion migration, leading to efficiency enhancement and improved ambient and thermal stabilities.