An article on measuring the delocalisation of charge carriers in organic semiconductors was recently published in Physical Chemistry Chemical Physics. In this paper we describe measurements for determining the spatial extent of charge carrier wave functions in small organic molecules and conjugated polymers which can be used as absorber materials in organic solar cells. The experiments are based on Electron Nuclear Double Resonance (ENDOR) spectroscopy, a combination of EPR  and NMR techniques. This work was realised in collaboration with colleagues from the King Abdullah University of Science & Technology in Saudi Arabia and the University of Massachusetts in Amherst.