Wide-Band-Gap (2.0 eV) Perovskite Solar Cells with a VOC of 1.325 V Fabricated by a Green-Solvent Strategy

Perovskite-based tandem solar cells are promising candidates for next-generation photovoltaic devices. However, the defects caused by ion migration cause a large deficit of open-circuit voltage (VOC) in conventional wide-band-gap perovskite films. Here, we present a new strategy that employs nontoxic acetic acid and isopropanol as solvents to deposit a perovskite film with a 2.0 eV band gap in an ambient atmosphere. The in situ formed acetate anions strongly stabilize the intrinsic defects in perovskite films. These features effectively improve the phase stability of 2.0 eV Cs0.2FA0.8PbI0.9Br2.1 perovskite, allowing the VOC to reach 1.325 V and the corresponding power conversion efficiency to reach 10.62%, which is close to the state-of-art performance of perovskite solar cells employing perovskite around a 2.0 eV band gap.