Annealing effect on photoluminescence and dopability of poly(3-octadecylthiophene) and its composites with fullerene

The effect of annealing on the optical properties and dopability of pristine and C60 — intercalated poly (3 -octadecylthiophene) (P3ODT) have been studied. After heat treatment of thin films of P3ODT increased structuring in the optical absorption spectra and also significant change in Franck-Condon factors in photoluminescence spectra were observed. The shape of PL spectra of heated P30DT become more wide. It is explained by better ordering and concentrating of polymer chains with long side groups (n=18) due to a “zipper effect”. The PL of P30DT(C60)y (with y=0.01) thin film after moderate annealing was recovered to initial intensity and the shape of spectra was changed to the original one of pristine P30DT. This behavior is explained by aggregation of C60 molecules into large clusters, so that PL quenching effect of single C60 molecules is suppressed