This is achieved by putting two polymer layers over the photovoltaic cell utilizing imprints of a regular DVD the researchers were able to produce slits which enhanced the efficiency of the device. The textured polymer layers acted as an electrode to both the TENG and the photovoltaic cell.
They conduct electricity when the water droplets fall on the device and the two layers come in contact with each other. The extra layers were transparent so the sunlight could be captured but the entire operation was not that efficient.
Hence the next challenge was to increase the efficiency of the entire device so that device could be feasible. This was achieved by adding an extra graphene layer. Scientists were able to bind ions to this layer which acts as a pseudocapacitor, hence a potential difference was achieved which in turn produced electricity.
The underlying concept for development of this technology comes from the principle of Lewis acid-base reaction or interactions. You see rainwater is an excellent reservoir of dissolved salts, it has lots of positive and negative ions. When these raindrops fall on the surface of graphene layer then a sort of pseudocapacitor is formed. Positive ions of sodium, calcium, and ammonium stimulate electrical flow. A layer of graphene can generate the fair amount of voltage on a rainy day, on full sun exposure the efficiency of the same reaches up to 7%. This technology can provide a great all-weather electricity source.
Rapid research and development are underway in this field. Some countries have even been able to develop regular solar panels with 20% efficiency. The future of this technology is yet to unfold.
All in all a very promising development in the field of solar energy. Hope we see its large-scale commercial application soon. Hope you liked the article.