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 (ψS) in p-channel polymer-based thin-film transistors (PTFT S). 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_{\rm 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× 10¹⁷[eV^-1cm^-3], kT_TD=035eV], N _DD=98× 10¹⁶[eV^-1cm^-3], and kT_DD=80[eV] over the bandgap.