The use of Kelvin Probe Force Microscopy to investigate PN junctions under illumination and electrical bias has been shown to be an effective way to analyze the electrical properties of solar cells at the nanoscale. We use it here, for the first time, on interdigitated back contact solar cells. Measurements are performed between the metallic fingers under an electrical bias in the dark and under illumination in open circuit conditions. Our results show that that KPFM could be used to identify and localize diodes resistance losses at the nanoscale.