Small-Molecule Hole Transport Materials for >26% Efficient Inverted Perovskite Solar Cells
Jie Zeng, Zhixin Liu, Deng Wang, Jiawen Wu, Peide Zhu, Yitian Bao, Xiaoyu Guo, Geping Qu, Bihua Hu, Xingzhu Wang, Yong Zhang, Lei Yan, Alex K.‐Y. Jen, Baomin Xu
Abstract
Chemically modifiable small-molecule hole transport materials (HTMs) hold promise for achieving efficient and scalable perovskite solar cells (PSCs). Compared to emerging self-assembled monolayers, small-molecule HTMs are more reliable in terms of large-area deposition and long-term operational stability. However, current small-molecule HTMs in inverted PSCs lack efficient molecular designs that balance both the charge transport capability and interface compatibility, resulting in a long-standing stagnation of power conversion efficiency (PCE) below 24.5%. Here, we report the comprehensive design of HTMs’ backbone and functional groups, which optimizes a simple planar linear molecular backbone with a high mobility exceeding 7.1 × 10 –4 cm 2 V –1 S –1 and enhances its interface anchoring capability. Owing to the improved surface properties and anchoring effects, the tailored HTMs enhance the interface contact at the HTM/perovskite heterojunction, minimizing nonradiative recombination and transport loss and leading to a high fill factor of 86.1%. Our work has overcome the persistent efficiency bottleneck for small-molecule HTMs, particularly for large-area devices. Consequently, the resultant PSCs exhibit PCEs of 26.1% (25.7% certified) for a 0.068 cm 2 device and 24.7% (24.4% certified) for a 1.008 cm 2 device, representing the highest PCE for small-molecule HTMs in inverted PSCs.