Solar cells can absorb and emit light

In a development that could lead to cheaper lasers, researchers have discovered that perovskite solar cells can emit as well as absorb light.

By sandwiching a thin layer of lead halide perovskite between two mirrors, researchers from Cambridge's Cavendish Laboratory produced an optically driven laser that effectively re-emitted 70% of absorbed light.

"This first demonstration of lasing in these cheap solution-processed semiconductors opens up a range of new applications," said Dr Felix Deschler, whoe led the research. "Our findings demonstrate potential uses for this material in telecommunications and for light emitting devices."

While most commercial solar cell materials need expensive processing before they show good luminescence, the new materials work well even when simply prepared as thin films using cheap scalable solution processing.

The researchers found that upon light absorption in the perovskite, two charges (electron and hole) form very quickly – within 1ps – but then take anywhere up to a few microseconds to recombine.

This is long enough for chemical defects to have ceased the light emission in most other semiconductors, such as silicon or gallium arsenide.

"These long carrier lifetimes, together with exceptionally high luminescence, are unprecedented in such simply prepared inorganic semiconductors," said Oxford University's Dr Sam Stranks, who helped with the research. "This has great implications for improvements in solar cell efficiency."