Interface Engineering of Air‐Stable n‐Doping Fullerene‐Modified TiO<sub>2</sub> Electron Transport Layer for Highly Efficient and Stable Perovskite Solar Cells
Bingjie Wang, Jianming Yang, Linyang Lu, Wei Xiao, Haiyan Wu, Shaobing Xiong, Jianxin Tang, Chun‐Gang Duan, Qinye Bao
Abstract
Abstract As one common electron transport material for planar n‐i‐p perovskite solar cell, titanium dioxide (TiO 2 ) compact layer has several challenging issues, such as surface hydroxyl groups, high defect density, and unmatched energy levels, causing severe energy loss and poor stability at contact. To solve these problems, the authors introduce a thin [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (PCBM) interlayer doped with an air stable n‐type dopant, 3‐dimethyl‐2‐phenyl‐2,3‐dihydro‐1H‐benzoimidazole (DMBI) to modify the TiO 2 surface. The state‐of‐the‐art characterizations demonstrate such modification significantly improves charge transfer at MAPbI 3 /TiO 2 interface together with smaller energy level offset, leading to suppressed charge recombination. High‐quality perovskite film with larger crystal grain size grows on the n‐doped PCBM/TiO 2 attributed to the better surface affinity. As a result, the average power conversion efficiency of perovskite solar cell exhibits a prominent improvement from 17.46% to 20.14%, with an enhancement in all device photovoltaic parameters. In addition, the stability of the device with n‐doped PCBM/TiO 2 is much better than that of the control device with the bare TiO 2 due to hydrophobicity nature of PCBM and low defect densities in the perovskite film and at the interface. This work indicates that many further device performance improvements should be conceivable by focusing on the perovskite interface.