Customized Multifunctional Additive Regulates 1.67 eV‐Wide‐Bandgap Perovskite Crystallization for Four‐Terminal Perovskite/Silicon Tandem Solar Cells

Abstract Wide‐bandgap (WBG) perovskite solar cells (PSCs, E _g > 1.6 eV), serving as the top cell in perovskite/silicon tandem solar cells (PSTSCs), play an indispensable role in absorbing high energy photons and increasing overall efficiency. However, WBG PSCs often suffer from severe light‐induced phase segregation and significant non‐radiative recombination losses due to uncontrolled rapid crystallization. Here, polyfluoride molecular additives are designed and incorporated via (diacetoxyiodo)benzene into WBG perovskite, to regulate crystallization process of perovskite films and thereby reduce defects. (Bis(trifluoroacetoxy)iodo)benzene (BTFIB) can passivate uncoordinated lead ions and iodide vacancies, thereby inhibiting phase separation caused by iodide migration and reducing non‐radiative recombination loss during charge transport. Moreover, the introduction of BTFIB can effectively moderate the film formation process and confer excellent hydrophobic properties to the films. Consequently, BTFIB‐based 1.67 eV‐WBG perovskite devices yield a champion efficiency of 23.05% (certified efficiency of 22.21%), enabling a 31.20% efficiency in four‐terminal PSTSCs, along with excellent open‐circuit voltage of 1.246 V and fill factor of 85.34%. After 2500 h of aging in a glovebox, the device retained 80% of its initial efficiency.