Photovoltaic solar-energy converting devices based on the mineral perovskite have within about two years of development reached efficiencies of 17 percent. Now, researchers at the universities of Cambridge and Oxford have demonstrated that they can also double as a laser. The teams of Cambridge's Richard Friend and Oxford's Henry Snaith have demonstrated that perovskite cells can absorb light as well as emitting it. They describe details of the new findings in the Journal of Physical Chemistry Letters. In their demonstration, the team sandwiched a thin layer of lead halide perovskite between two mirrors to produce an optically driven laser that can re-emit up to 70% of the light it absorbs.