Abstract Films of conjugated polymer blends were studied by NMR relaxometry in order to improve the understanding of the nanomorphology and segmental chain mobility. Whereas optical microscopy was applied to obtain a rough impression about the surface morphology, the T1H and T2H NMR relaxation decay times were determined in the solid state (13C-CP/MAS and 1H-wideline NMR) to judge the homogeneity of the phase morphology, to estimate the size of phase separated molecular domains and to compare the local segmental chain mobility. Besides blend composition, important parameters investigated are the film processing technique (dropcasting vs. spincoating), the casting solvent and the casting substrate.