Vacuum-deposited perovskite photovoltaics for highly efficient environmental light energy harvesting

The performance of vacuum-deposited organometal halide perovskite devices under low-intensity illumination was investigated. The low defect density of the vacuum-deposited perovskite thin film facilitates the development of a high performance device with low-cost C60 as the electron transporting layer, which is superior to solution-processed cells made by a 2-step spin-casting method with expensive fullerene derivatives. The small-area vacuum-deposited devices exhibited high power conversion efficiencies and output power densities of up to 30.1% and 94.9 μW cm−2 at 1000 lux and 28.5% and 18.1 μW cm−2 at 200 lux, respectively. The large-area vacuum-deposited devices with an active area of 5.68 cm2 showed high reproducibility and exhibited high power conversion efficiencies and output power densities up to 24.9% and 77.6 μW cm−2 at 1000 lux and 21.9% and 13.8 μW cm−2 at 200 lux, respectively. Moreover, the small- and large-area devices also showed good stability and a negligible efficiency decrease in one year. The high performance and high stability results indicate that vacuum-deposited perovskite photovoltaics are one of the most promising energy harvesters for low-power electronics in the future.