Effects of hole and electron trapping on organic field-effect transistor transfer characteristic

Routine organic field-effect transistor measurements are performed at negative and positive gate voltages leading to the occurrence of both hole and electron trapping. Despite this fact, the big majority of studies have focused either on hole trapping or on electron trapping but not on both at the same time. This paper presents the influences of trapped electron concentration ntrap and trapped hole concentration ptrap on the transfer characteristic (TC) features: onset voltage, hysteresis and transconductance, i.e. apparent mobility. Some effects are common to both charge types: (1) hysteresis is due to a combination of lower detrapping rate than sweep rate for ntrap and ptrap, (2) the transconductance is decreased by the super-linear VG dependence of ptrap and by ntrap detrapping. One effect is opposite to both charge types: ptrap (ntrap) shifts the onset voltage towards negative (positive) value. We consider that the knowledge of trap-induced effects from both charge types is useful for correctly interpreting and understanding TCs.