Highly Transparent, Scalable, and Stable Perovskite Solar Cells with Minimal Aesthetic Compromise

Transparent photovoltaics (TPVs) can be integrated into the surfaces of buildings and vehicles to provide point‐of‐use power without impacting aesthetics. Unlike TPVs that target the photon‐rich near‐infrared portion of the solar spectrum, TPVs that harvest ultraviolet (UV) photons can have significantly higher transparency and color neutrality, offering a superior solution for low‐power electronics with stringent aesthetic tolerance. In addition to being highly transparent and colorless, an ideal UV‐absorbing TPV should also be operationally stable and scalable over large areas while still outputting sufficient power for its specified application. None of today's TPVs meet all these criteria simultaneously. Here, the first UV‐absorbing TPV is demonstrated that satisfies all four criteria by using CsPbCl2.5Br0.5 as the absorber. By precisely tuning the halide ratio during thermal co‐evaporation, high‐quality large‐area perovskite films can be accessed with an ideal absorption cutoff for aesthetic performance. The resulting TPVs exhibit a record average visible transmittance of 84.6% and a color rendering index of 96.5, while maintaining an output power density of 11 W m−2 under one‐sun illumination. Further, the large‐area prototypes up to 25 cm2 are demonstrated, that are operationally stable with extrapolated lifetimes of >20 yrs under outdoor conditions. Thermal co‐evaporation is used to access a unique perovskite composition, CsPbCl2.5Br0.5, which is scalable, thick, structurally uniform, and sufficiently robust to survive the deposition of indium tin oxide. Employing these active layers, the functional transparent photovoltaics are demonstrated to have record transparency, near‐perfect color neutrality, decent power density, scalability, and high operational stability, offering a superior solution for low‐power electronics with stringent aesthetic tolerance.