Organic Solar Hits New Landmark
Experts are starting to believe that the future of solar energy lies not in silicon, but in organic solar cells—also known as organic photovoltaics (OPV). OPVs, which are made from carbon and plastic, are cheaper to make and have far more flexible engineering applications.
OPVs can be made with compounds that are dissolvible in ink, which is then printed on to a diverse range of materials. This allows engineers to build semi-transparent solar cells into windowpanes, bend them to build on the roofs of aesthetically pleasing architecture and even put them into glasses’ lenses for users to solar charge their phone on the go.
Despite the advantages, OPVs aren’t normally used in solar energy on account of their low efficiency rates. Where silicon photovoltaics convert between 18 to 22 percent of solar energy into electricity, OPVs have only been able to achieve half that rate.
Researchers have been making big leaps toward higher-efficiency OPVs this year. In April, a team from the University of Michigan broke records with a commercially viable cell that boasted 15 percent efficiency, comparable to some of the silicon cells on the market.
The Chinese team’s results, which were published last week in Science, were achieved by rethinking OPVs from the ground up. The team applied a tandem cell system, meaning that they built two solar cell devices in the same structure to target two different wavelengths of sunlight, thereby increasing the yield.
“We have two layers of active materials; each layer can absorb different wavelengths of light. That means you can use sunlight in the wider wavelengths more efficiently, and this can generate more current," said Yongshen Chen, PhD, who led the study.
Chen believes the results mean that solar cells using the tandem solution may be on the market in under five years, as the commercial materials are already widely available. According to him, OPVs are similar to organic light-emitting diodes, which are currently used in high-end TVs.