Light emitting ambipolar field-effect transistors of 2,5-bis(4-biphenyl)bithiophene single crystals with anisotropic carrier mobilities

Ambipolar carrier injection is observed in organic field-effect transistors (FETs) based on 2,5-bis(4-biphenylyl)bithiophene single crystals. The device shows carrier mobilities of 0.04 and 0.02 cm2 V s for holes and electrons, respectively. Strong edge emission is observed, and the emission zone shifts upon the applied gate voltage. Hysteresis is found mainly in the ambipolar and electron-dominated regions. The electron mobility is significantly more sensitive to the transport direction than the hole mobility, suggesting that tuning the transport direction is very important to realize amplified spontaneous emission in organic FETs.