Abstract
Copper is a traditional dopant for many types of polycrystalline thin-film CdTe photovoltaic devices. However, Cu can easily distribute through the depth and breadth of the device, segregating at interfaces or grain boundaries and leading to metastability of the device. Directly correlating Cu-related defect species to the local (i.e. nanoscale) charge transport in CdTe devices remains challenging due to relatively low Cu concentrations in the CdTe layer. Using nanoscale X-ray microscopy, we simultaneously probe both the elemental copper distribution and electrical performance of the device in cross-section. Complementary charge transport modelling delineates the possible defect distributions that can exist under low and high Cu loading, and how these defects interact with charge carriers at different depths of the device.