Atomic — Scale study of model CdTe grain boundaries

Poly-crystalline CdTe-based thin film photovoltaic (PV) devices are the forerunners in commercialized solar cell technology. Despite the commercial success, best laboratory cells achieve ~21.5% power conversion efficiency and hence are still ~10% short of theoretical limit. In this collaborative research project we investigate effects of the grain boundaries via wafer-bonded CdTe bicrystals. Lifetime measurements are carried out using two-photon absorption, while atomic resolution imaging and first-principles calculations are used to correlate the results. Here we present fundamental atomic-scale studies of several model grain boundaries.