A Targeted Functional‐Group Integration Strategy for Modulating Wide‐Bandgap Perovskites Toward Efficient Silicon/Perovskite Tandem Photovoltaics

ABSTRACT Wide‐bandgap (WBG) perovskites featuring 1.65–1.70 eV bandgaps are highly desirable light‐harvesting layers to construct high‐performance tandem photovoltaics. However, the complex multi‐component precursor system, especially the asymmetric nucleation of I‐rich and Br‐rich phases during film formation, often leads to difficulties in crystallization control, in turn leading to incomplete precursor reaction, inhomogeneous crystallization, and a high density of film defects. Herein, we introduce a multifunctional additive, 2,3,4,5,6‐pentafluoroanilino(oxo)acetic acid (5FNOA), which features a distinctive combination of functional groups that simultaneously modulates the crystallization kinetics of WBG perovskites and passivates defects. 5FNOA interacts with perovskite precursors via multiple functional groups to stabilize colloidal precursors and selectively retarding Br‐rich phase nucleation while synchronizing it with PbI X , thereby enabling well‐controlled crystallization and preventing uncontrolled, rapid crystal growth. Consequently, a single‐junction 1.66 eV WBG perovskite solar cell (PSC) delivers a power conversion efficiency (PCE) of 24.04%. A two‐terminal perovskite/silicon tandem solar cell (TSC) achieves an outstanding PCE exceeding 33% and exhibits significantly enhanced operational stability. This work offers a versatile multifunctional molecular engineering strategy for high‐quality WBG perovskites toward efficient silicon/perovskite TSCs.