Halide insertion regulation for efficient and stable wide-bandgap perovskite photovoltaics

Wide-bandgap (WBG) perovskite solar cells (PSCs) are employed for tandem solar cells. Understanding the crystallization mechanism of mixed-halide WBG perovskite will contribute to achieving the high-performance photovoltaics. Herein, we demonstrate that the asynchronous halide insertion is accompanied by random crystal facets and orientations, restricting the efficient carrier extraction. Guided by density functional theory calculations, we construct a π-conjugated molecular wall structure using o-phenylenediamine (OPD). The molecular wall at the grain boundary induces templated perovskite crystallization through the ortho-diamine group, enabling synchronous [PbBr6]4- and [PbI6]4- halide insertion. The OPD-treated perovskite film exhibits a preferred (100) facet and a highly vertical orientation. Benefited from the improved carrier extraction, the resulting WBG PSC (1.69 eV) achieves a power conversion efficiency of 24.13% (certified 23.43%), representing one of the highest values among WBG PSCs. Meanwhile, the improved perovskite crystal quality ensures the enhanced operational stability of the PSCs. Understanding the crystallization mechanism of mixed-halide wide-bandgap perovskites is critical to improve the performance of tandem solar cells. Here, the authors introduce ophenylenediamine to construct a π-conjugated molecular wall structure, achieving a maximum solar cell efficiency of 24.13%.