Inside a solar cell, sunlight excites electrons. But these electrons often don't last long enough to go on to power cell phones or warm homes. In a promising new type of solar cell, the solar-excited electrons have better odds going on to work. Why? A team led by UVA researchers discovered the dominant mechanism for the higher carrier lifetime that is responsible for the superior hybrid organic-inorganic perovskite solar cell performance. The mechanism involves screening excited charge carriers by the rotating positively charged (cationic) organic molecules in the crystal.