Enhanced Charge-Carrier Mobility in High-Pressure-Crystallized Poly(3-hexylthiophene)

Enhanced charge-carrier mobility in high-pressure-crystallized poly(3-hexylthiophene) (P3HT) was studied. P3HT of larger molecular weights is considered to ensure that the macromolecules are of a length above the range where they naturally form extended-chain crystals, in the regime where chain folding sets in, and chain entanglements form in their melt or concentrated solutions. The calorimetric studies reveal a distinct increase of the melting temperature of the high-pressure-crystallized polymer, from 235 to 248°C for P3HT. The results also show that pressure-induced crystallization result in an increase of the crystal thickness of up to 65% for the higher molecular weight material, while an increase of more than 15% is observed for the P3HT of 60 kg mol-1. For the lower-molecular-weight material, the enhancement in charge-carrier mobility in pressure solidified materials is found to be less pronounced.