Regulation of Wide Bandgap Perovskite by Rubidium Thiocyanate for Efficient Silicon/Perovskite Tandem Solar Cells

Abstract Developing high‐quality wide bandgap (WBG) perovskites with ≈1.7 eV bandgap ( E _g ) is critical to couple with silicon and create efficient silicon/perovskite tandem devices. The sufferings of large open‐circuit voltage ( V _OC ) loss and unstable power output under operation continuously highlight the criticality to fully develop high‐quality WBG perovskite films. In this study, rubidium and thiocyanate as additive regulators in WBG perovskites are incorporated, significantly reducing non‐radiative recombination, ion‐migration, and phase segregation. The optimized 1.66 eV E _g perovskite solar cells achieved state‐of‐art 1.3 V V _OC (0.36 V deficit), and delivered a stabilized power conversion efficiency of 24.3%, along with good device stability (20% degradation (T ₈₀ ) after over 994 h of operation under 1 sun at ≈65°C). When integrated with a flat front side silicon cell, silicon/perovskite two‐terminal tandem device (30% efficient) is obtained with a 1.97 V V _OC , and T ₉₀ operational lifetime of more than 600 h at room temperature.