Chinese researchers develop solar cell that can charge in rain

We are always in the search alternative sources of energy, mostly from renewable resources. In practice, that usually translates to solar and wind power, mostly the former. But while the sun is almost always available, at least during the day, it can sometimes be hidden for hours under a torrent of rain. To get past at least that situation, a group of researchers from the Ocean University of China and Yunnan Normal University are developing a new time of solar cell that can generate electricity even without the sun. At least as long as there is rain.

The prototype solar cell the almost magical properties of graphene with the ironically impure nature of rain water. Unlike pure water, rain water is composed of bits of salt that separate into positive and negative ions. Graphene, on the other hand, allows electrons to flow freely on its surface. In the presence of water, it lets positive ions pair with negative electrons to produce electricity as the end product.

When rain water comes in contact with graphene, the water becomes infused with positive ions. The graphene, on the other hand, is enriched with delocalized (freely moving) electrons. This double layer of electrons and positive ions produce what is called a pseudocapacitor. This leads to the production of voltage and current which, in turn, can be used to charge batteries or power equipment.

A solar cell that can harness both sun and rain, depending on the weather, would definitely be a dream come true. The researchers have tested a prototype using a thin film of graphene layered on top of a solar cell and slightly salty water to take the place of rain. The prototype was able to produce hundreds of microvolts of electricity which, though minuscule, is still promising. Further refinement is all that's needed to perfect these "all-weather" solar cells.