Effects of film morphology on ambipolar transport in top-gate-type organic field-effect transistors using poly(9,9-dioctylfluorene-co-bithiophene)

► Structure ordering in F8T2 films has a strong influence on ambipolar characteristics. ► Improving the interface geometry of the F8T2 film led to an increase in mobility. ► Improving the interface geometry led to the appearance of ambipolar characteristics. ► Ambipolar F8T2 devices exhibited yellow EL emissions. ► Devices exhibited maximum external quantum efficiency of approximately 0.2%.