RF sputtered CdS films as independent or buffered electron transport layer for efficient planar perovskite solar cell

Metal sulfide has the potential to take the place of high temperature sintered TiO₂ as electron transportation layer for perovskite solar cell (PSC) with improved light stability and suppressed hysteresis. In this work, CdS films were used as independent or buffered electron transport layer for planar perovskite solar cell by a low-temperature RF sputtering method for the first time. The effects of surface roughness and optical absorption of CdS films on the photovoltaic performance of PSCs were discussed. The PSC with sputtered CdS film shows a higher open-circuit voltage (V_oc) and efficiency of 13.17% than high temperature sintered TiO₂ ETL (12.71%). Moreover, a RF sputtered CdS buffer layer between TiO₂ and perovskite could tune the conduction band edge of TiO₂ and perovskite and passivating the surface defects. Time resolved photoluminescence results indicate the RF sputtered CdS film buffer layer could accelerate charge transportation and a higher conversion efficiency over 16% has thus been achieved, with enhanced air stability and minimized hysteresis. These findings offer new research directions for low-temperature sputtered metal sulfide film as a promising electron transport material for stable and high efficient planar perovskite solar cell.