Investigation of the effects of substrate annealing on the properties of polymer blends

In this manuscript, we investigated the effect of substrate annealing prior to the deposition of the active layer on the morphological, structural and opto-electrical properties of two variations of organic polymer blends of poly (3-hexylthiophene):C60 fullerene and poly (3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester films using atomic force microscopy, field emission scanning microscopy, x-ray diffraction and Hall effect measurements. P3HT films deposited on pre-annealed substrates exhibit an enhancement in the crystallization, and an increase in the electrical conductivity and Hall mobility of p-type P3HT. The microscopic morphology reveals self-assembled fibrillar structures due to the suppressed growth of fullerenes clusters induced by the controlled evaporation rate of the solvent. It is proposed that pre-substrate annealing controls the crystallization of P3HT, the phase separation and diffusion of the acceptor material (C60 or PCBM).