Molecular Bridge in Wide‐Bandgap Perovskites for Efficient and Stable Perovskite/ Silicon Tandem Solar Cells

Abstract Perovskite/silicon tandem solar cells (TSCs) attract intensive attention because of their potential to deliver power conversion efficiencies (PCE) beyond those of their single‐junction counterparts. However, the performance and stability of tandem devices are limited by defect‐assisted non‐radiative recombination and light‐induced halide segregation in wide‐bandgap (WBG) perovskite sub‐cells. Here, 2‐aminoethanesulfonamide hydrochloride (AESCl), with multi‐point chelation sites and bridging capability, is incorporated into a 1.68 eV WBG perovskite to comprehensively passivate defects at grain boundaries and surfaces. As a result, AESCl‐treated perovskite films show suppressed halide segregation and a champion WBG single‐junction solar cell achieves an impressive efficiency of 22.80% with an open‐circuit voltage of 1.286 V due to reduced non‐radiative recombination. The efficient WBG perovskite sub‐cells enable perovskite/silicon TSCs to reach a champion PCE of 30.36% over 1 cm 2 . Moreover, the tandem devices retain over 96% of their initial efficiency after operation for 1068 h under continuous AM 1.5G illumination at 25 °C in ambient air.