Optimizing Crystallization in Wide-Bandgap Mixed Halide Perovskites for High-Efficiency Solar Cells.

Wide-bandgap perovskites have attracted considerable attention due to their adjustable bandgap properties, making them ideal candidates for top subcells in tandem solar cells (TSCs). However, wide-bandgap (WBG) perovskites often face challenges such as inhomogeneous crystallization and severe non-radiative recombination loss, leading to high open-circuit voltage (V OC ) deficits and poor stability. To address these issues, we introduce a multifunctional phenylethylammonium acetate (PEAAc) additive that enhances uniform halide phase distribution and reduces defect density in perovskite films by regulating the mixed-halide crystallization rate. This approach successfully developed efficient WBG perovskite solar cells (PSCs) with reduced V OC loss and enhanced stability. By applying this universal strategy to the FAMACsPb(I 1- x Br x ) 3 system with a range of bandgaps of 1.72, 1.79, 1.85, and 1.92 eV, we attained power conversion efficiencies (PCE) of 21.3%, 19.5%, 18.1%, and 16.2%, respectively. These results represent some of the highest PCEs reported for the corresponding bandgaps. Furthermore, integrating the WBG perovskite with low-bandgap organic photovoltaics, we achieved an impressive PCE of over 24% for two-terminal perovskite/organic TSCs, with a record V OC of ∼ 2.2 V. This work establishes a foundation for addressing phase separation and inhomogeneous crystallization in Br-rich perovskite components, paving the way for the development of high-performance WBG PSCs and TSCs. This article is protected by copyright. All rights reserved.