Lead halide perovskites are already famous for their ability to harvest solar energy, and now researchers are starting to show that the semiconductors make for promising lasers. Last year, British researchers demonstrated that lasers made with perovskite thin films and powered by light had a quantum efficiency of about 70%, meaning a laser emitted seven photons for every 10 absorbed. Chemists led by Song Jin of the University of Wisconsin, Madison, and Xiaoyang Zhu of Columbia University say they have now pushed that efficiency to nearly 100% using perovskite nanowires (Nat. Mater. 2015, DOI: 10.1038/nmat4271). The team grew the wires by first depositing a film of lead acetate on a glass substrate and submerging the film in a concentrated methylammonium halide solution. Lead slowly dissolved in the solution, allowing single-crystal lead halide perovskite nanowires to grow. Each nanowire’s high crystalline quality contributes to its quantum efficiency, which Zhu says is so high it’s “unheard of” in other semiconductor materials. The researchers are now working to power their lasers with electricity rather than light, which could pave the way to miniaturized optoelectronic devices.