Fully Transfer Characteristic-Based Technique for Surface Potential and Subgap Density of States in p-Channel Polymer-Based TFTs

We report a fully subthreshold current-based technique for characterization of subgap density of states [DOS:g(E)] with consistent mapping of the surface potential (ψ
_S
) in p-channel polymer-based thin-film transistors (PTFTS). Initially, we propose a technique for extraction of the DOS over the bandgap using the gate voltage (V
_GS
)-dependent ideality factor [m(V
_GS
)] from the transfer characteristics of the PTFTs under subthreshold operation. We also propose a technique for a consistent nonlinear mapping of V
_GS
to the subgap energy level by converting m(V
_GS
) to ψ
_S
. Through combining the two methods, the exponential tail and deep g(E) are obtained to be N
_TD
=1·1×10
¹⁷
[eV
^-1
·cm
^-3
], kT
_TD
=0·035 [eV], N
_DD
=9·8×10
¹⁶
[eV
^-1
·cm
^-3
], and kT
_DD
=0·80 [eV] over the bandgap.