Green anti-solvent engineering for high-efficiency and environmentally friendly perovskite solar cells.

Flat and dense perovskite films with low defect density are essential for high-performance perovskite solar cells (PSCs). Anti-solvent-assisted crystallization (ASAC) is one of the effective ways to obtain high-quality perovskite films with low cost and simple operation. However, most of the traditional anti-solvents such as chlorobenzene, toluene, and diethyl ether have strong toxicity, which would be harmful to people's physical and mental health. It can be anticipated that when these toxic anti-solvents are widely applied in the industry, they will have destructive effects on humans and the environment, which is contrary to the current promotion concepts of green environmental protection. In September 2015, the United Nations Development Program regulated the Sustainable Development Goals (SDGs) for Mankind, which clearly emphasized the use of economically viable clean energy that was compatible with the goals for climate action, good health and well-being. So the development of non-hazardous green anti-solvents is an important direction in the research field of PSCs. In this review paper, the outstanding research achievements on green anti-solvents in recent years are summarized, including different types of perovskite films using different green anti-solvents with/without additives, the physical and chemical properties of different green anti-solvents, and their effects on the performance of perovskite films and PSCs. Moreover, five types of non-anti-solvent green preparation methods regulated by physical processes are also assessed. It provides references for the manufacturing of efficient, stable, low-cost and environmentally friendly perovskite devices.