Surface Passivation for Enhancing Photovoltaic Performance of Carbon-Based CsPbI3 Perovskite Solar Cells

Although hole transport layer (HTL)-free carbon-based CsPbI3 perovskite solar cells (CsPbI3 C-PSCs) possessed a best band-gap of CsPbI3 as absorber material, the photovoltaic conversion efficiency (PCE) and stability were suppressed by the poor-quality perovskite film and the invasion of moisture in the atmosphere. Herein, 4,4'-dimethoxytriphenylmethyl chloride (DMT-Cl) passivator not only increased the grain sizes of CsPbI3 crystals through crystal regrowth, but also passivated the surface defects. A champion PCE of 10.88% and a large open circuit voltage (V-oc) of 0.96 V were obtained in CsPbI3 C-PSC passivated by DMT-Cl. The unencapsulated CsPbI3 C-PSCs remained a PCE of approximately 60% for 600 h in air at a relative humidity (RH) of 20-30%, indicating an improved stability.