IMPACT OF THE UNIVERSAL MOBILITY LAW ON POLYCRYSTALLINE ORGANIC DEVICE AND CIRCUIT OPERATION

摘要

We have developed an analytical model for polycrystalline-based organic thin-film transistors (OTFTs) that employs, as far as possible, new concepts on carrier injection to the conventional polysilicon model. The drain current equations, both in diffusion and drift regimes, predict the voltage and temperature dependencies on the various device and circuit parameters. Interestingly, upon direct comparison with previously developed disordered model, similarities between the two are not thought to be coincidental. The effect of gate voltage on surface potential is affected by the Fermi level pinning in the grain boundary, which is assumed to consist of mainly disordered material. This work also highlights the problem of using drift mobility, as an organic circuit design parameter, and consequently alternative quantities are proposed for simpler circuits such as an inverter. Upon validation of the model, relatively good fits are obtained with the experimental data on TIPS-based TFTs. The divergence at low drain voltages are thought to be associated with short channel and/or high contact resistance effects.