Functionalized Ionic Liquid-Crystal Additive for Perovskite Solar Cells with High Efficiency and Excellent Moisture Stability
Xuefeng Xia, Jiayi Peng, Qixin Wan, Xiaofeng Wang, Zhiping Fan, Jie Zhao, Fan Li
Abstract
Organic–inorganic hybrid perovskite solar cells (PSCs) have emerged as a promising candidate for next-generation solar cells. However, the limited stability of PSCs hampers their practical applications. In this work, for the first time, a functionalized π-conjugated ionic liquid crystal (ILC), 4′-(N,N,N-trimethyl ammonium bromide hexyloxy)-4-cyanobiphenyl (6CNBP-N), is developed as a novel chemical additive to obtain CH3NH3PbI3 (MAPbI3) PSCs with high efficiency and excellent moisture stability. This 6CNBP-N ILC possesses the characteristics of ionic liquids and liquid crystals. The inclusion of the 6CNBP-N ILC can effectively improve the quality and stability of perovskite films, reduce the trap-state densities, and promote the carrier transport induced by the cyano group (C≡N), a rod-like π-conjugated biphenyl mesogenic unit and quaternary alkylammonium cations (R4N+) in 6CNBP-N. Through this functionalized ILC engineering strategy, the power conversion efficiency (PCE) of PSCs is greatly increased from 18.07% for the control PSC to 20.45% for the PSC with 6CNBP-N along with the depressed hysteresis effect and enhanced moisture stability of PSCs. Our work provides a new strategy for designing functionalized additives for high-performance PSCs.