Influence of hole and electron trapping on gate field dependent mobility and its degradation in organic field effect transistors

• Degradation of mobility at higher gate voltages.
• Caused by hole and electron trapping effect.
• Increase in hole trap concentration delays the onset point of degradation.
• Passivation of hydroxyl groups on dielectric surface with suitable polymer results in constant mobility at higher gate voltages.

Influence of hole and electron trapping effect on the gate field dependence of mobility, especially degradation at higher gate voltages, in organic field effect transistors is identified. Extent of mobility degradation was found to be dependent on the starting value of the gate voltage sweep. Both electron and hole trap concentrations are found to cause degradation in mobility with the former dominating over the latter. Significant increase in hole trap concentration causes slow increase in mobility for a certain span of gate voltage before shifting the onset point of degradation to much higher gate voltages. The interplay between the trap density, carrier density, mobility and the effective gate field decides the extent of degradation. Reduction of both hole and electron trap concentration by passivating the trap centres on the dielectric surface with suitable polymers resulted in constant mobility at higher gate voltages.