Wide‐bandgap (WBG) perovskites are essential components for all‐perovskite tandem solar cells, yet they often suffer from substantial open‐circuit voltage ( V OC ) deficits and uncontrolled crystallization kinetics. Herein, we employ a coordination engineering strategy with a multifunctional additive, 4‐(Trifluoromethyl) benzene‐1‐sulfonyl chloride (BSCF 3 ), to optimize 1.77 eV WBG perovskite films. Detailed spectroscopic characterizations reveal that the –SO 2 Cl group acts as a Lewis base to coordinate with Pb 2+ ions and the strongly electronegative –CF 3 group forms hydrogen bonds with formamidinium (FA + ) cations. These synergistic effects regulate the subsequent nucleation and crystallization kinetics. Driven by this controlled growth process, the resulting films exhibit enlarged grain sizes and suppressed residual PbI 2 phases. This enhanced structural integrity, in turn, minimizes the trap‐state density and significantly mitigates nonradiative recombination at the grain boundaries. As a result, the inverted 1.77 eV WBG perovskite solar cells achieve a champion power conversion efficiency (PCE) of 19.81% with a high V OC of 1.32 V. Furthermore, the optimized monolithic all‐perovskite tandem cells deliver a remarkable PCE of 27.26%. Under continuous 1‐sun illumination in a nitrogen atmosphere, both the single‐junction and tandem devices retain approximately 80% of their initial efficiencies after 1000 and 300 h aging, respectively.
Huang et al. (Wed,) studied this question.