Effect of structure on semiconducting properties of a small molecule n-type organic semiconductor: Phenyl-C61-butyric acid methyl ester

The fullerene-based derivative phenyl-C61-butyric acid methyl ester (PCBM) has attracted attention as an n-type transistor channel and an organic photovoltaic material due to its solution processability, stability, and high electron mobility. However, disorder in solution-processed PCBM thin films makes understanding of charge carrier transport mechanisms difficult. We have fabricated PCBM-based field effect transistors and improved device performance by reducing electron trapping at the dielectric-semiconductor interface and improving charge carrier injection. Single-wall carbon nanotubes were successfully integrated into conventional gold electrodes to improve injection efficiency. Meyer-Neldel behavior has been investigated in a study of charge carrier transport in PCBM thin films. Crystallization of PCBM was observed during the measurement. We find that charge carriers hop between molecules in mostly amorphous regions from 145 to 240 K. The transport is facilitated by the formation of more crystallized regions when samples are heated as high as 240 K. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

The fullerene-based derivative PCBM has been widely studied as an n-type transistor channel and an organic photovoltaic material. However, disorder in solution-processed PCBM thin films complicates the understanding of charge carrier transport mechanisms. In this study, PCBM-based field effect transistors were fabricated, and the device performance was improved by reducing electron trapping and improving charge carrier injection. Single-wall carbon nanotubes were integrated into gold electrodes, which enhanced injection efficiency. Meyer-Neldel behavior was observed, and charge carrier transport was found to occur mainly in amorphous regions with hopping transport between molecules.