In photosynthesis, plants that are exposed to sunlight use carefully organized nanoscale structures within their cells to rapidly separate charges, pulling electrons away from the positively charged molecule that is left behind, and keeping positive and negative charges separated. This is the key to making the process so efficient.
To capture energy from sunlight, conventional rooftop solar cells use silicon, a fairly expensive material. There is currently a big push to make lower-cost solar cells using plastics, rather than silicon, but today’s plastic solar cells are relatively inefficient, in large part because the separated positive and negative electric charges often recombine before they can become electrical energy.
‘Modern plastic solar cells don’t have well-defined structures like plants do because we never knew how to make them before,’ Tolbert said. ‘But this new system pulls charges apart and keeps them separated for days, or even weeks. Once you make the right structure, you can vastly improve the retention of energy.’
The researchers are already working on how to incorporate the technology into actual solar cells. For now, though, the UCLA research has proven that inexpensive photovoltaic materials can be organized in a way that greatly improves their ability to retain energy from sunlight.