Concentration-dependent mobility in organic field-effect transistors probed by infrared spectromicroscopy of the charge density profile

TL;DR

Infrared spectromicroscopy of organic FETs reveals that charge mobility depends on charge density, showing power-law behavior indicative of activated transport in disordered systems, providing insights inaccessible by traditional contact methods.

Contribution

This study introduces infrared spectromicroscopy as a novel, contactless method to probe charge density profiles and transport properties in organic FETs, revealing density-dependent mobility.

Findings

Mobility in P3HT FETs follows a power-law density dependence.

Infrared imaging effectively probes transport characteristics.

Activated transport occurs in disorder-induced tails of the density of states.

Abstract

We show that infrared imaging of the charge density profile in organic field-effect transistors (FETs) can probe transport characteristics which are difficult to access by conventional contact-based measurements. Specifically, we carry out experiments and modeling of infrared spectromicroscopy of poly(3-hexylthiophene) (P3HT) FETs in which charge injection is affected by a relatively low resistance of the gate insulators. We conclude that the mobility of P3HT has a power-law density dependence, which is consistent with the activated transport in disorder-induced tails of the density of states.