Efficient CdTe photovoltaics by co-passivating grain boundaries

Efficiency improvements in poly-CdTe can be achieved by fundamental understanding of the role of impurity atoms that can effectively passivate grain boundaries. In the present work, we investigated CdTe grain boundaries using TEM and SMIM, and studied effect of Se and Cu passivation on CdTe grain boundaries using first principles density functional theory (DFT) calculations. Se and Cu segregation to grain boundaries are thermodynamically feasible. Both Cu and Se can effectively reduce midgap states, but most improvement was achieved when Cu and Se are co-doped together, which is predicted to increase the PV efficiency of CdTe. The study we presented can be extended to dopant studies in other solar cell materials.