Characterization of charge transport in organic field effect transistors using modulated amplitude reflectance spectroscopy

Due to their mechanical flexibility and low cost, organic semiconductors are used as the active element in a range of optoelectronic devices; however, low charge mobility in these materials limits further application. In this work, we use modulated amplitude reflectance spectroscopy (MARS) to generate high-resolution, spatially-mapped images of the carrier distribution in operating organic polymer field effect transistors. In the region outside of the contacts channel, carrier mobility values extracted from the measured drift distance of the carriers from the contacts are consistent with mobilities measured using conventional bulk transfer curve analysis. MARS can be used to investigate charge carrier mobility and its dependence on charge carrier density and electric field, as well as to examine the effects of device geometry, defects, and electrical contacts on charge mobility and device efficiency. Supported by NSF award #1919282.