# Chasing the killer phonon mode for the rational design of low disorder, high mobility molecular semiconductors

## TL;DR

This study identifies the dominant phonon mode affecting charge transport in high mobility organic semiconductors, providing insights for designing materials with lower disorder and higher mobility.

## Contribution

It combines advanced quantum simulations with experimental techniques to pinpoint the key phonon mode influencing electron-phonon coupling in organic semiconductors.

## Key findings

- Long-axis sliding motion is the primary phonon mode contributing to thermal disorder.
- This mode accounts for over 80% of the total thermal disorder in some molecules.
- The insights enable rational design guidelines for high mobility molecular semiconductors.

## Abstract

Molecular vibrations play a critical role in the charge transport properties of weakly van der Waals bonded organic semiconductors. To understand which specific phonon modes contribute most strongly to the electron-phonon coupling and ensuing thermal energetic disorder in some of the most widely studied high mobility molecular semiconductors, state-of-the-art quantum mechanical simulations of the vibrational modes and the ensuing electron phonon coupling constants are combined with experimental measurements of the low-frequency vibrations using inelastic neutron scattering and terahertz time-domain spectroscopy. In this way, the long-axis sliding motion is identified as a killer phonon mode, which in some molecules contributes more than 80% to the total thermal disorder. Based on this insight, a way to rationalize mobility trends between different materials and derive important molecular design guidelines for new high mobility molecular semiconductors is suggested.

---
Source: https://tomesphere.com/paper/1903.10852