Bication Thiocyanate Salts for Advanced Performance of Wide-Band Gap Perovskite Solar Cells

Abstract

Organohalide perovskite materials with a high band gap of over 1.65 eV are employed in tandem photovoltaic cells, but higher defect density, deeper trap states, and halide separation in the perovskites limit the performance of all of the tandem cells. In this study, a thiocyanate (SCN)-based ionic liquid, 1-butyl-3-methylimidazolium thiocyanate (BMI-Th), was added to the perovskite material to improve its performance and stability. BMI-Th-added perovskite solar cells (PSCs) display higher power conversion efficiency (PCE) but insufficient stability at high temperatures. When Pb(SCN)2 was additionally incorporated with BMI-Th, the passivation of defects was strengthened, thereby resulting in enhanced PCE and stability at high temperatures. PSCs with BMI-Pb bication SCN additives achieved improved performance with higher open-circuit voltage and lower hysteresis as well as long-term operational stability under AM 1.5 G 1 sun illumination at 60 °C without any encapsulation.