The focus of this work is on the nano-scale characterization of transition metal oxides employed as carrier selective contacts in crystalline silicon (c-Si) solar cells using crosssectional transmission electron microscopy (TEM). Both electronselective (titanium dioxide, TiO 2 ) and hole-selective (molybdenum oxide, MoO x ; tungsten oxide, WO x textbf) contacts were investigated. High-resolution TEM (HRTEM) images were obtained with a FEI Tecnai F30 TEM.