Lead-halide perovskite solar cells have seen rapid gains in efficiency and stability over the past few years. And many solar energy researchers have come to see this technology—based on a type of organic-inorganic crystal—as one of today’s most promising emerging solar energy technologies. However, the typical lead-halide perovskites are only a narrow class of a broad group of materials known as hybrid organic-inorganic semiconductors—or HOIS. Consequently, a new Energy Frontier Research Cent...