Room-Temperature Molten Salt for Facile Fabrication of Efficient and Stable Perovskite Solar Cells in Ambient Air

Organic-inorganic hybrid perovskites have recently attracted extensive attention for their potential uses in photovoltaics. However, solvent-handling issues and toxicology concerns represent a major challenge in solution-processed perovskite thin films. Here, we demonstrate that an environmentally- and industrially friendly room-temperature molten salt (RTMS), methylammonium acetate (MAAc), can produce high-quality perovskite films in ambient air, leading to the development of perovskite solar cells (PSCs) with 20% efficiency and stability for more than 1,000 h. MAAc is a universal solvent for all common perovskite-based salts and may open up the potential of using RTMS solvent for facile fabrication of PSCs. Moreover, this work represents a new direction in the development of efficient and stable PSCs and other optoelectronic devices.