Tiny solar cells could soon charge electric vehicles while on the road

Researchers claim to have hit on the right combination of solar cell type and battery to charge an electric vehicle battery with higher efficiency than ever before. The team behind the research says the system could soon make it possible to attach small cells to a car that will charge the vehicle while being driven – on a sunny day, at least.

The researchers from Case Western Reserve University wired four perovskite solar cells in series to directly photo-charge lithium batteries with 7.8 percent efficiency, which they believe to be the most efficient configuration reported to date.

"We found the right match between the solar cell and battery... Others have used polymer solar cells to charge lithium batteries, but not with this efficiency," said Liming Dai, the leader of the research team, adding that the coupling appears to have outperformed all other reported pairings of photo-charging components and compatible batteries or super-capacitors.

Perovskite has been one of the most promising solar cell technologies to emerge of late, thanks to its ability to convert a broader spectrum of sunlight to electricity when compared to silicon-based cells. The crystalline material has a structure identical to the mineral of the same name, and its potential for highly efficient power conversion and a quick payback in terms of energy savings over traditional power sources have made it one of the fastest growing sectors in the solar power field. As a sort of added bonus, it has even been found to emit light at night, functioning similar to an LED.

Dai's lab created cells with three layers converted into a single perovskite film and then wired four of the 1 mm square cells in series, achieving a solar-to-electric power conversion efficiency of 12.65 percent.

When hooked up to charge small coin-sized lithium-ion batteries, the team achieved a conversion and storage efficiency of 7.8 percent and maintained it over a number of cycles.

"We envision, in the not too distant future, this is a system that you could have at home to refuel your car and, eventually, because perovskite solar cells can be made as a flexible film, they would be on the car itself," said contributing author Jiantie Xu.

This would seem to make the technology a perfect fit for cars with a more traditional look than the Immortus solar sports car, whose every available sky-facing surface is covered in 7 sq m (75 sq ft) of solar photovoltaic paneling.

The research was published in the most recent issue of Nature Communications.

Source: Case Western Reserve University