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

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 (T₈₀) 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 T₉₀ operational lifetime of more than 600 h at room temperature.