Nanoscale mapping of Cu doping effects in photovoltaic Sb2Se3 films

Antimony selenide (Sb2Se3) has emerged as one of the promising alternative p-type absorbers for thin-film photovoltaics due to its earth abundance, favourable band gap, and high absorption coefficient. However, its practical efficiency remains still limited by crystallographic anisotropy and intrinsically low carrier density, motivating the search for effective doping strategies. Copper (Cu) has recently been introduced as a dopant in Sb2Se3, yet the nanoscale details of its incorporation and distribution at relatively high concentrations (3-5%) remain unclear. Here, we employ conductive atomic force microscopy (C-AFM) in combination with AFM topography to directly compare undoped and Cu-doped Sb2Se3 thin films prepared by radio-frequency magnetron sputtering. Correlated current and morphology mapping reveal an approximately two-order-of-magnitude increase in conductivity upon Cu doping, with a relatively homogeneous distribution across grains in device-relevant thick films. Characterization of thinner films can provide details also on other nanosized features, like localized conductivity hotspots and potential percolative shunts at grain boundaries. Such nanoscale insights are essential for a comprehensive understanding of this dopant behavior and, at the same time, highlight a novel C-AFM-based approach to study doping effects in semiconductor thin films.