Highly Efficient and Reliable Semitransparent Perovskite Solar Cells via Top Electrode Engineering

Abstract Transparent electrodes are essential to allow optical transparency for realizing semitransparent perovskite solar cells (ST‐PSCs). This study addresses gallium‐ and titanium‐doped indium oxide (IO:GT) between the electron transport layer (ETL) and top electrode to potentially replace conventional indium tin oxide (ITO) used in inverted ST‐PSCs. The shallower work function (−4.23 eV) of IO:GT than that (−4.69 eV) of conventional ITO contributes to suppressing the formation of the Schottky barrier and enhancing the charge transport at the ETL/cathode interface. By adopting IO:GT, the ST‐PSC exhibits an enhancement in power conversion efficiency (PCE) from 8.59% to 17.90% (certified 17.53%) with an average visible transmittance (AVT) of 21.9%, which is the record PCE at similar AVT among all ST‐PSCs reported to date. Moreover, combining these ST‐PSCs as the top cell, a four‐terminal perovskite–perovskite tandem solar cell is realized, showing a high PCE of 23.35%. Furthermore, the stability of the ST‐PSCs is confirmed excellent, maintaining over 96% of the initial PCE after 1864 h (≈77 days) in air ambient without encapsulation, which is better than the device employing a metal cathode. Therefore, these results demonstrate that the adoption of IO:GT can be a promising route for efficient and stable inverted ST‐PSCs with preferred transparency.