As useful and ubiquitous as solar energy is becoming, it still has one major Kryptonite: gloomy weather. Now, a team of Chinese engineers has developed a hybrid solar cell that can produce electricity come rain or shine, using the triboelectric effect to harvest energy from the movement of raindrops on its surface.

Triboelectric nanogenerators (TENGs) create a charge from the friction of two materials rubbing together, which you may recognize as static electricity. It could find eventual practical uses in harvesting energy from movement or vibrations through clothing, car wheels, floors, or touchscreens.

In this case, the researchers tapped into the motion of raindrops rolling off the surface of a solar cell. To do so, they added two polymer layers to form a TENG on top of a photovoltaic cell. The top layer consists of a polymer called polydimethylsiloxane (PDMS), while the lower layer is made of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). To improve the performance of both layers, the polymers are first textured with grooves by imprinting them with the pattern from the data side of DVDs.