# Critical Evaluation of Organic Thin-Film Transistor Models

## TL;DR

This paper introduces a two-step method to evaluate the adequacy of organic TFT models by analyzing their electrical measurements across different channel lengths, revealing that current models often fail to capture key dependencies.

## Contribution

A novel technique for assessing the validity of transistor models based on channel-length dependence analysis of electrical measurements.

## Key findings

- State-of-the-art models do not accurately reproduce channel-length dependence.
- The technique reveals the need for improved models considering charge-carrier-density effects.
- Organic TFT models require enhancements to better reflect physical phenomena.

## Abstract

Thin-film transistors (TFTs) represent a wide-spread tool to determine the charge-carrier mobility of materials. Mobilities and further transistor parameters like contact resistances are commonly extracted from the electrical characteristics. However, the trust in such extracted parameters is limited, because their values depend on the extraction technique and on the underlying transistor model. We propose a technique to establish whether a chosen model is adequate to represent the transistor operation. This two-step technique analyzes the electrical measurements of a series of TFTs with different channel lengths. The first step extracts the parameters for each individual transistor by fitting the full output and transfer characteristics to the transistor model. The second step checks whether the channel-length dependence of the extracted parameters is consistent with the model. We demonstrate the merit of the technique for distinct sets of organic TFTs that differ in the semiconductor, the contacts, and the geometry. Independent of the transistor set, our technique consistently reveals that state-of-the-art transistor models fail to reproduce the correct channel-length dependence. Our technique suggests that contemporary transistor models require improvements in terms of charge-carrier-density dependence of the mobility and/or the consideration of uncompensated charges in the transistor channel.