Accurate analytical approximation of the OTFTs surface potential by means of the Lagrange Reversion Theorem

Surface-potential-based mathematical models are among the most accurate and physically based compact models of Thin-Film Transistors (TFTs) and, in turn, of Organic Thin-Film Transistors (OTFTs), available today. However, the need for iterative computations of the surface potential limits their computational efficiency and diffusion in CAD applications. The existing closed-form approximations of the surface potential are based on regional approximations and empirical smoothing functions that could result not enough accurate to model OTFTs and, in particular, transconductances and transcapac- itances. In this paper we present an accurate and computationally efficient closed-form approximation of the surface potential, based on the Lagrange Reversion Theorem, that can be exploited in advanced surface-potential-based OTFTs and TFTs device models.