Chinese researchers have introduced a new approach for making an all-weather solar cell that is triggered by both sunlight and raindrops. To convert solar energy to electricity, the team developed a highly efficient dye-sensitized solar cell. In order to allow rain to produce electricity as well, they coated this cell with a whisper-thin film of graphene.

Graphene electrodes obtain power from the impact of raindrops. Raindrops are not pure water – they contain salts that dissociate into positive and negative ions. The positively charged ions bind to the graphene surface. At the point of contact between the raindrop and the graphene, the water becomes enriched in positive ions, and the graphene becomes enriched in delocalized electrons. The difference in potential associated with this phenomenon produces a voltage and current.

Source