Rainy city

Hybrid solar cell generates electricity from falling raindrops

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A team of Chinese researchers has demonstrated a method which enables solar cells to generate electricity from the falling of raindrops, improving their efficiency and allowing them to generate energy even at night.

While recent leaps and bounds in solar technology have boosted its popularity – particularly as governments seek alternatives to fossil fuels to reduce carbon emissions and fulfil the requirements of the Paris Agreement – some issues with the technology remain.

One of the greatest drawbacks is the still-limited efficiency of solar cells, particularly during cloudy and rainy weather when little sunlight can reach the cells. This is a significant problem in countries with less than paradisiacal weather, such as the UK.

However, a team of researchers based at Soochow University in China has developed hybrid solar cells which are capable of generating energy even during a rainy spell.

Previous attempts to improve the efficiency of solar cells under rainy conditions have involved the addition of a pseudocapacitor (a component of a supercapacitor) or a triboelectric nanogenerator (TENG, a useful device which converts mechanical energy into electricity) to an existing solar cell. While helpful, these approaches have proved complex to assemble and result in a bulky final product.

The Soochow University team took an alternative approach to the problem, imprinting two polymers with grooves by simply placing them onto DVDs. Adding this texture resulted in a boost to the triboelectric performance of one of the polymers, i.e. improving the efficiency of the conversion of external mechanical energy of the falling raindrops into electrical energy.

Meanwhile, the other polymer is placed between the TENG and the solar cell and acts as a mutual electrode for the devices, conducting energy from the TENG to the cell.

As the two polymers are transparent, they do not prevent the cell continuing to generate energy from sunlight in addition to falling rain. Such a hybrid solar cell would be capable of generating energy even during a dark and rainy light thanks to the incorporation of the TENG.

“The hybrid energy harvesting system […] can combine the advantages of high current level of a solar cell and high voltage of a TENG device, promising an efficient approach to collect energy from the environment in different weather conditions,” the researchers wrote in ACS Nano.

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