Three engineers including one of Indian-origin from Stanford University have invented a novel transparent coating that cools solar cells to boost solar panel efficiency. The tests showed that the coating allowed only visible light to pass through to the solar cell, filtering out the thermal radiation, keeping the temperature as low as 23 degrees Fahrenheit.

The latest development builds on work past year when the trio developed an ultrathin material that radiated infrared heat directly back toward space without warming the atmosphere.

“Our thermal overlay allows sunlight to pass through, preserving or even enhancing sunlight absorption, but it also cools the cell by radiating the heat out and improving the cell efficiency”, he explained.

Solar cells are less efficient when they’re hot, which poses an obvious problem – solar cells sit in direct sunlight and get incredibly hot as a result. The newly created silica overlay is placed over a conventional solar cell. It also has the potential to be applied to vehicle paintwork, without affecting aesthetics.

Solar panels must face the sun directly to function optimally, but at the cost of heating up, which causes it to loose efficiency.

In the case of the newest materials, the researchers found that clear and dry environments are ideal – the same kind of environments were large solar arrays are located. For a fairly normal crystalline silicon solar cell with 20 per cent efficiency, the researchers claim that sort of temperature reduction could equate to an increase in the absolute cell efficiency by over 1 per cent – not to be sniffed at if the film can be made affordably.

They believe they can scale things up so commercial and industrial applications are feasible, perhaps using nanoprint lithography, which is a common technique for producing nanometre-scale patterns.

Solar panels are a great way to capture energy from the sun but they’re far from flawless .

“This is not necessarily the only way”, said Aaswath P. Raman, co-author of the study. “I am optimistic”, Raman noted. “Thermal overlays can help with passive cooling, but it’s a problem if they’re not fully transparent”, said doctoral candidate Linxiao Zhu. Therefore, any overlay would have to be transparent, or to be tuned to absorb only light beyond the visible spectrum.