For what is believed to be for the first time, the device physics based modeling approach to derive the generic model current equations of organic thin film transistor (OTFT) is described. Firstly, the current model equation is derived by considering the dependence of mobility on gate voltage and doping density, which is more realistic and relevant to organic materials containing TFTs. To model small molecule or polymer TFT, the potential drop across contacts is taken into account as contacts are not ohmic due to some morphological disorders. Further the effect of contact resistance is included and accordingly the generic model current equation is modified. It shows a good agreement of proposed current equation with simulated results which validates the proposed OTFT model from ohmic to saturation regime. Moreover, the analytical model is used to extract the contact and channel resistances in linear and saturation region and these resistances are verified through potential cut line (PCL) and transmission line methods (TLM). The extracted parameters are not only used to verify the electrical characteristics but also exhibit insight on contact potential, charge injection and transport phenomenon for organic TFT operation.
Study of Contact Resistance on Organic Thin-Film Transistor with Surface Treatments
