All-thiophene donor-acceptor blends: photophysics, morphology and photoresponse

We report on the photophysical, morphological and photoresponse properties of blends of a regioregular poly(3-hexylthiophene) (P3HT) as the electron-donor and a quinquethiophene-S,S-dioxide (T5OHM) as the electron-acceptor. A scanning force microscopy study on 100 nm thick blended films revealed the occurrence of a notable phase segregation between the two components and a remarkable tendency of the acceptor molecule to form micrometre sized architectures characterized by sharp edges within the amorphous matrix of P3HT. X-Ray diffraction studies confirmed the high degree of crystallinity of T5OHM in the blended films. The interaction of the oligomer with the polymer resulted in an enhanced photoinduced charge separation, leading to a sixty-fold increase of the power conversion efficiency in the blended cells with respect to the pristine device based on neat P3HT.