Electric Field Effects on the Optoelectronic Properties of Fluorinated Heptyl-Bicyclohexyl-Biphenyl: A TD-DFT...

In this study, the electronic, optical, and dielectric properties of fluorinated heptyl-bicyclohexyl-biphenyl are investigated using density functional theory (DFT) and time-dependent DFT. The ground-state geometry is optimized and confirmed to be stable by vibrational analysis, while the low-lying excited states are mainly characterized by ππ* transitions localized on the biphenyl core. In addition, a high energy excited state is identified with the largest oscillator strength (f = 0.8994) at 6.57 eV, corresponding to a πσ* intramolecular charge transfer transition from the biphenyl moiety to the bicyclohexyl substituent. External electric fields are applied along the molecular long axis, corresponding to the direction of maximum polarizability, as well as along two perpendicular directions. The strongest effects on absorption spectra, dipole moment, polarizability, and the HOMO-LUMO gap occur when the field aligns with the molecular long axis. In particular, a dramatic polarizability jump from 317 to 2990 Bohr³ accompanies the field-induced closure of the HOMO-LUMO gap, evidencing substantial charge redistribution and enhanced mixing of frontier molecular orbitals. In contrast, the responses induced by perpendicular field orientations remain comparatively weak.