Researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) developed a breakthrough in energy-efficient phototransistors.    Such devices could eventually help computers process visual information more like the human brain and be used as sensors in things like self-driving vehicles.   The structures rely on a new type of semiconductor—metal-halide perovskites—which have proven to be highly efficient at converting sunlight into electrical energy and have sh...