Charge-transfer excitations in molecular donor-acceptor complexes within the many-body Bethe-Salpeter approach

TL;DR

This paper demonstrates that the many-body GW and Bethe-Salpeter approach accurately predicts low-lying charge-transfer excitations in molecular donor-acceptor complexes, matching experimental data and enabling ab initio studies of photovoltaic processes.

Contribution

It shows that the GW and Bethe-Salpeter methods can reliably compute charge-transfer excitations in complex molecular systems without adjustable parameters.

Findings

Mean average error of 0.1-0.15 eV in excitation energies

Excellent agreement with time-dependent DFT studies

Applicable to both finite and extended systems

Abstract

We study within the perturbative many-body $GW$ and Bethe-Salpeter approach the low lying singlet charge-transfer excitations in molecular donor-acceptor complexes associating benzene, naphtalene and anthracene derivatives with the tetracyanoethylene acceptor. Our calculations demonstrate that such techniques can reproduce the experimental data with a mean average error of 0.1-0.15 eV for the present set of dimers, in excellent agreement with the best time-dependent density functional studies with optimized range-separated functionals. The present results pave the way to the study of photoinduced charge transfer processes in photovoltaic devices with a parameter-free \textit{ab initio} approach showing equivalent accuracy for finite and extended systems.