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

Organic semiconductors (OSCs) have received significant 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 TIPS-TAPs substituted with F and Cl exhibit excellent agreement with the experimental values, while the simulation overestimates the electron mobility for TIPS-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, which reduces the electron transfer integral and increases the reorganization energy. While molecular packing is widely recognized as a dominant factor in charge transport in OSCs, our study highlights the crucial role of electronic effects in charge transport in OSCs. This study provides new insights into the mechanisms underlying charge transport in OSCs.