https://phys.org/news/2018-07-boost-quality-perovskites.html

In a paper published online this spring in the journal Nature Photonics, scientists at the University of Washington report that a prototype semiconductor thin-film has performed even better than today's best solar cell materials at emitting light.

"It may sound odd since solar cells absorb light and turn it into electricity, but the best solar cell materials are also great at emitting light," said co-author and UW chemical engineering professor Hugh Hillhouse, who is also a faculty member with both the UW's Clean Energy Institute and Molecular Engineering & Sciences Institute. "In fact, typically the more efficiently they emit light, the more voltage they generate."