Room temperature, air crystallized perovskite film for high performance solar cells

For the first time, room temperature heating free growth and crystallization of perovskite films in ambient air without the use of thermal annealing is reported. Highly efficient perovskite nanorod-based solar cells were made using ITO/PEDOT:PSS/CH₃NH₃PbI₃ nanorods/PC₆₀BM/rhodamine/Ag. All the layers except PEDOT:PSS were processed at room temperature thereby eliminating the need for thermal treatment. Perovskite films were spin coated inside a N₂ filled glovebox and immediately were taken outside in air having 40% relative humidity (RH). Exposure to humid air was observed to promote the crystallization process in perovskite films even at room temperature. Perovskite films kept for 5 hours in ambient air showed nanorod-like morphology having high crystallinity, with devices exhibiting the highest PCE of 16.83%, which is much higher than the PCE of 11.94% for traditional thermally annealed perovskite film based devices. It was concluded that moisture plays an important role in room temperature crystallization of pure perovskite nanorods, showing improved optical and charge transport properties, which resulted in high performance solar cells.