Light-emitting organic field-effect transistors based on highly luminescent single crystals of thiophene/phenylene co-oligomers

Abstract

A series of thiophene/phenylene co-oligomers containing π-conjugated anthracene, naphthalene, and biphenyl central cores have been developed as new organic laser active materials. Light-emitting organic field-effect transistors (LE-OFETs) based on 2,6-bis(5-phenylthiophen-2-yl)anthracene (BPTA), 2,6-bis(5-phenylthiophen-2-yl)naphthalene (BPTN), and 2,6-bis(5-phenylthiophen-2-yl)-1,1′-biphenyl (BPTB) single crystals were fabricated. A clear laser oscillation was observed for BPTN and BPTB single crystals. Especially for BPTB, a low amplified spontaneous emission threshold of 1.8 ± 0.2 μJ cm⁻² was achieved. In addition, all of the devices showed ambipolar transport characteristics, in which both electron and hole carriers are transported in a single FET device, and electroluminescence was clearly observed. An obvious difference in the light emission direction was observed for LE-OFET devices, which is attributed to the difference in transition dipole moment arrangement of individual molecules within the crystal.