Scientists at the Energy Department’s National Renewable Energy Laboratory (NREL) are studying what may seem paradoxical – certain defects in silicon solar cells may actually improve their performance.   The findings run counter to conventional wisdom, according to Pauls Stradins, the principal scientist and a project leader of the silicon photovoltaics group at NREL.   Deep-level defects frequently hamper the efficiency of solar cells, but NREL theoretical research suggests that defec...