In this article we highlight few recent works performed making use of KPFM [1] with the aim of getting fundamental information on the nanoscale electrical and electronic properties of organic and supramolecular materials effectively employed for real opto-electronic devices, and to correlate them with their behavior on a macroscopic scale [2]. After a brief description of the scanning probe technique, this article describes the electrical nanoscale characterization of organic bulk heterojunctions for solar cells when tested under an additional stimulus, ie. light.