Graphene has been called upon to further improve solar cells by providing these devices with the capability to generate power when it’s raining. An all-weather solar cell triggered by both sunlight and raindrops has been developed by Chinese researchers who combined an electron-enriched graphene electrode with a dye-sensitized solar cell.

Solar cell produces power from sun and raindrop impacts. Image source: Wiley-VCH.Solar cell produces power from sun and raindrop impacts. Image source: Wiley-VCH. Graphene is a two-dimensional form of carbon in which the atoms are bonded into a honeycomb arrangement. It can be prepared by the oxidation, exfoliation and subsequent reduction of graphite. The material conducts electricity and is rich in electrons that can move freely across the entire layer (delocalized). In aqueous solution, graphene can bind positively charged ions with its electrons (Lewis acid-base interaction), a property used in graphene-based processes to remove lead ions and organic dyes from solutions.

This phenomenon inspired researchers from Ocean University of China and Yunnan Normal University to use graphene electrodes to obtain power from the impact of raindrops, which contain salts that dissociate into positive and negative ions. The positively charged ions, including sodium, calcium and ammonium ions, can 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. This results in a double-layer made of electrons and positively charged ions, a feature known as a pseudocapacitor. The difference in potential associated with this phenomenon is sufficient to produce a voltage and current.

The solar cell can be excited by incidental light on sunny days and raindrops on rainy days, yielding a solar-to-electricity conversion efficiency of 6.53% under AM 1.5 irradiation and current over microamps, as well as a voltage of hundreds of microvolts by simulated raindrops.

To contact the author of this article, email GlobalSpeceditors@globalspec.com