Time Dependent Density Functional Theory calculations of the optical properties of charge-transfer complexes

TL;DR

This paper uses time-dependent density functional theory to calculate and analyze the optical properties and charge transfer mechanisms of specific donor-acceptor complexes, matching experimental spectra and exploring stoichiometry effects.

Contribution

It presents novel TD-DFT calculations of charge transfer complexes, providing insights into their optical spectra and charge transfer degrees across different stoichiometries.

Findings

Good match between calculations and experimental spectra

Low energy CT absorption bands appear at dimer/tetramer stage

Charge transfer varies with stoichiometry

Abstract

Charge transfer complexes are materials with a wide range of interesting optical and electronic properties. They have seen a great deal of research over the past decade, both in device development as well as research to elucidate the underlying mechanisms of charge transfer and transport. Here we present time dependent density-functional theory (TD-DFT) calculations of the energy levels of the donor-acceptor complexes perylene-TCNQ (7,7,8,8-tetracyanoquinodimethane) and hexamethylbenzene-chloranil. The calculations show a good match to the experimentally measured optical absorption spectra, and indicate that low energy CT absorption bands appear at the dimer/tetramer stage of cocrystal formation. We also report the degree of charge transfer for these complexes in various stoichiometries and compare them.