New solar cell turns raindrops into electricity

Researchers from two Chinese universities have developed a solar cell that can produce electricity from light and water, enabling a solar panel that works in the sun or rain.

The scientists from Ocean University of China in Qingdao and Yunnan Normal University in Kunming developed a highly efficient and flexible dye-sensitized solar cell and then coated that cell with a one atom-thick layer of electron-enriched graphene.

The new all-weather solar cells can be excited by light on sunny days and raindrops on rainy days, yielding an optimal "solar-to-electric conversion efficiency of 6.53% under sunlight as well as a voltage of hundreds of microvolts by simulated raindrops.

"Graphene is known for its conductivity, among many other benefits. All it takes is a mere one-atom thick graphene layer for an excessive amount of electrons to move as they wish across the surface," the researchers wrote in the journal Angewandte Chemie.

"In situations where water is present, graphene binds its electrons with positively charged ions. Some of you may know this process to be called the Lewis acid-base interaction," the researchers said.

Ocean University of China/Yunnan Normal University

The structures and components of the bi-triggering solar cells that can be excited by sunlight and rain: (a) front irradiation, (b) rear irradiation.

The graphene converts each drop of rain into microamps and raindrops into hundreds of microvolts.

With only a 6.53% light/water electricity conversion rate, the new all-weather panels are far from perfect. Today's typical solar panels have a 15% solar energy conversion rate. The best panels, which are still in laboratories, have a 22% conversion rate. So the all-weather panels are highly inefficient, and graphene is an extremely expensive material to manufacture.

However, for areas with greater rain accumulation such as the U.K., the panels do offer an alternative to solar panels that would otherwise suffer a 10% to 25% decrease in energy production.

"All-weather solar cells are promising in solving the energy crisis," the researchers wrote.

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