Self-cooling solar cells boost power, last longer

Scientists, including one of Indian-origin, may have overcome one of the major hurdles in developing high-efficiency, long-lasting solar cells - keeping them cool, even in the blistering heat of the noonday Sun.
By adding a specially patterned layer of silica glass to the surface of ordinary solar cells, researchers led by Shanhui Fan, an electrical engineering professor at Stanford University has found a way to let solar cells cool themselves by shepherding away unwanted thermal radiation.
Solar cells are among the most promising and widely used renewable energy technologies on the market today. Though readily available and easily manufactured, even the best designs convert only a fraction of the energy they receive from the Sun into usable electricity.

Part of this loss is the unavoidable consequence of converting sunlight into electricity. A surprisingly vexing amount, however, is due to solar cells overheating.
Under normal operating conditions, solar cells can easily reach temperatures of 55 degrees Celsius or more.
These harsh conditions quickly sap efficiency and can markedly shorten the lifespan of a solar cell. Actively cooling solar cells, however would be prohibitively expensive and at odds with the need to optimise exposure to the Sun.

By embedding tiny pyramid- and cone-shaped structures on an incredibly thin layer of silica glass, the researchers found a way of redirecting unwanted heat - in the form of infrared radiation - from the surface of solar cells, through the atmosphere, and back into space.

"Our new approach can lower the operating temperature of solar cells passively, improving energy conversion efficiency significantly and increasing the life expectancy of solar cells," said Linxiao Zhu, a physicist at Stanford and lead author on the research paper.
"Our method of carefully altering the layers that cover and enclose the solar cell can improve the efficiency of any underlying solar cell. This makes the design particularly relevant and important," said Aaswath Raman, a postdoctoral scholar at Stanford and co-author on the paper.
The research appears in the journal Optica.