Ambipolar conductivity in organic field-effect transistors based on 1,7-bis(9-ethyl-3-carbazolyl) N,N′-2-ethyl hexyl perylene bisimide under the light illumination

• The light induced ambipolarity in organic transistors was studied.
• Impedance spectroscopy of barrier structure was used to explain the obtained effect.
• Enhancement of the injection of holes in the OFET under illumination was observed and discussed.

The occurrence of light induced ambipolar conductivity in organic transistors based on 1,7-bis(9-ethyl-3-carbazolyl) N,N′-2-ethyl hexyl perylene bisimide (BCEHPB) was studied. It is shown that under illumination the output characteristics are transformed into superposition of standard saturated behavior for one carrier at high gate voltage and a superlinear current increase at low gate voltage and high source–drain voltage due to injection of the opposite (hole) carrier. The influence of injection of holes from metal electrodes by impedance spectroscopy barrier structure BCEHPB/Ag was studied to explain this effect. Increasing the injection of holes in the transistor under illumination can be interpreted as a result of the devastation of the interface trap states.