Improved sublimation growth of single crystals of thiophene/phenylene co-oligomers

We have improved the sublimation recrystallization method using a handmade sublimation apparatus and optimizing various physical conditions. The improved apparatus comprises two closely aligned heaters and enables us to grow the large thiophene/phenylene co-oligomer (TPCO) crystals of high quality. We found it essential and effective for the crystal growth to adjust temperatures of these heaters and their temperature difference of ca. 40–50 °C. We fabricated organic field effect transistor (OFET) devices with the resulting crystals of a TPCO. Those devices show the p-type FET characteristics. The field effect mobilities increased with smaller thicknesses of the crystals; the maximum mobility recorded was 0.021 cm2/Vs.