Light-emitting field-effect transistors made of single crystals of an ambipolar thiophene/phenylene co-oligomer

We have developed an ambipolar thiophene/phenylene co-oligomer (TPCO) by introducing the trifluoromethyl group and the methoxy group to molecular terminals of the parent (unsubstituted) TPCO molecule. The crystals of the compound exhibit the ambipolar carrier transport on the field-effect transistors with homogeneous Au electrodes and heterogeneous MgAg and Au electrodes. The latter device definitively emits the light by applying sinusoidal-wave and square-wave alternating-current (AC) voltages to the gate electrode. Time-dependent emission measurements indicate that major emissions take place twice during each period of the AC gate bias.