Phase‐Stable Wide‐Bandgap Perovskites for Four‐Terminal Perovskite/Silicon Tandem Solar Cells with Over 30% Efficiency

Abstract Wide‐bandgap perovskite solar cells (PSCs) with an optimal bandgap between 1.7 and 1.8 eV are critical to realize highly efficient and cost‐competitive silicon tandem solar cells (TSCs). However, such wide‐bandgap PSCs easily suffer from phase segregation, leading to performance degradation under operation. Here, it is evident that ammonium diethyldithiocarbamate (ADDC) can reduce the detrimental I 2 back to I − in precursor solution, thereby reducing the density of deep level traps in perovskite films. The resultant perovskite film exhibits great phase stability under continuous illumination and 30–60% relative humidity conditions. Due to the suppression of defect proliferation and ion migration, the PSCs deliver great operation stability which retain over 90% of the initial power conversion efficiency (PCE) after 500 h maximum power point tracking. Finally, a highly efficient semitransparent PSC with a tailored bandgap of 1.77 eV, achieving a PCE approaching 18.6% with a groundbreaking open‐circuit voltage ( V OC ) of 1.24 V enabled by ADDC additive in perovskite films is demonstrated. Integrated with a bottom silicon solar cell, a four‐terminal (4T) TSC with a PCE of 30.24% is achieved, which is one of the highest efficiencies in 4T perovskite/silicon TSCs.