Imprisoning 2H intermediate phases in blade-coated wide-bandgap perovskites for efficient all-perovskite tandem solar cells
Dexin Pu, Xuhao Zhang, Hongyi Fang, Weichen Shen, Guoyi Chen, Weiqing Chen, Peng Jia, Guang Li, Hongling Guan, Lishuai Huang, Yuan Zhou, Jiahao Wang, Wenwen Zheng, Weiwei Meng, Guojia Fang, Weijun Ke
Abstract
Scalable fabrication of high-efficiency all-perovskite tandem solar cells (TSCs) remains challenging due to notable voltage deficits in wide-bandgap perovskite solar cells, primarily driven by severe halide segregation during the large-scale blade coating process. Here, we introduce 4-aminobenzylphosphonic acid as a functional "2H-imprison" additive that selectively bypasses the formation of the 2H phase (an iodine-rich structure) and promotes the direct crystallization of the desired 3C phase, resulting in a homogeneous phase and halide distribution. Consequently, blade-coated 1.77-electron volt-bandgap perovskite solar cells achieved a power conversion efficiency (PCE) of 20.35% (certified 19.72%) with an open-circuit voltage of 1.35 volts for a ~0.07-square centimeter aperture area, while 1.02-square centimeter devices delivered a PCE of 19.00%. Furthermore, the corresponding blade-coated two- and four-terminal all-perovskite TSCs demonstrated high PCEs of 27.34 and 28.46%, respectively. This study reveals the origins of phase segregation during blade coating and provides a viable strategy to mitigate it, paving the way for scalable and high-efficiency TSCs.