16.10% Carbon‐Based Hole‐Transport‐Layer‐Free CsPbI 2 Br Solar Cells Enabled by Uracil‐Based Additives
Hongyan Cheng, Zhengjun Meng, Xueyan Ma, Hai Liu, Wenxuan Li, Linfeng Kang, Xuan Qi, Diao Yang, Yali Li, Yujun Fu, Deyan He, Junshuai LiABSTRACT
Carbon‐based hole‐transport‐layer (HTL)‐free CsPbI 2 Br solar cells present a promising balance among efficiency, stability and cost. Nevertheless, their performance is still restricted by bulk and interfacial defects, as well as energy level mismatch between CsPbI 2 Br and its neighboring layers. Herein, a series of uracil‐based additives, including uracil, 5‐cyanouracil (5‐CU) and 5‐nitrouracil (5‐NU), are introduced into CsPbI 2 Br to construct dipolar molecular bridges that can simultaneously passivate defects (i.e., uncoordinated Pb 2+ and mobile halide ions in CsPbI 2 Br and uncoordinated Sn 4+ on the surface of SnO 2 ), improve crystallinity, and regulate interfacial energy level alignment. It is further found that the most polar 5‐NU exhibits the best ability to realize these functions. The 5‐NU‐optimized device thus achieves a leading power conversion efficiency of 16.10%, with an exceptional open‐circuit voltage of 1.345 V, significantly reduced hysteresis and excellent operational stability.