Band-like transport down to 20 K in organic single-crystal transistors based on dioctylbenzothienobenzothiophene

Band-like transport has been realized down to 20 K in solution-processed single-crystal transistors based on dioctylbenzothienobenzothiophene. The mobility increases from 16 to 52 cm2/V s as the temperature is lowered from 300 to 80 K. An abrupt mobility drop is observed around 80 K, but even below 80 K, gradually increasing mobility is restored again down to 20 K instead of thermally activated transport. From the observation of a shoulder structure in the transfer curve, the mobility drop is attributed to a discrete trap state.