Effect of Halogen Substituents on Charge Transport Properties of n-type Organic Semiconductors: A Theoretical Study

TL;DR

This theoretical study examines how halogen substituents influence charge transport in n-type organic semiconductors, revealing electronic effects are crucial alongside molecular packing.

Contribution

It demonstrates the significant impact of halogen electronic effects on charge mobility, challenging the traditional focus solely on molecular packing in OSCs.

Findings

Computed mobilities match experimental data for F and Cl substitutions.

Fluoride's electron-withdrawing effect reduces electron transfer.

Electronic effects are vital in charge transport mechanisms.

Abstract

Organic semiconductors (OSCs) have received much attention as promising materials for electronic devices. In this study, we investigate the impact of halogen groups on the charge transport properties of n-type OSC-6,13 bis ((triisopropylsilyl) ethynyl)-5,7,12,14-tetraazapentacene (TIPS-TAP). The computed mobilities for TAPs substituted with F and Cl exhibit excellent agreement with the experimental values, while the simulation overestimates the electron mobility for TAP. Interestingly, the mobility of TIPS-TAP-4F is significantly lower than that of TIPS-TAP-4Cl/Br, despite their similar packing structures. This discrepancy can be attributed to the strong electron-withdrawing effect of fluoride, leading to reduced electron transfer integrals and increased reorganization energy. While molecular packing is widely accepted as a dominant factor in charge transport in OSCs, our study highlights the essential role of electronic effects in OSC charge transport. This study provides new insights into the understanding of the charge transport mechanism in OSCs.