Resonant hot charge-transfer excitations in fullerene-porphyrin complexes: a many-body Bethe-Salpeter study

TL;DR

This study uses many-body Green's function methods to analyze excitations in a fullerene-porphyrin complex, revealing hot charge-transfer states that facilitate charge separation.

Contribution

It provides a detailed theoretical analysis of charge-transfer excitations and hot states in a donor-acceptor complex using GW and Bethe-Salpeter approaches, supporting a hot charge-transfer scenario.

Findings

Lowest excitation is a charge-transfer state matching DFT results.

Identifies hot electron-hole states resonant with intramolecular excitations.

Supports the role of delocalized hot states in charge separation.

Abstract

We study within the many-body Green's function GW and Bethe-Salpeter approaches the neutral singlet excitations of the zinctetraphenylporphyrin and C70 fullerene donor-acceptor complex. The lowest transition is a charge-transfer excitation between the donor and the acceptor with an energy in excellent agreement with recent constrained density functional theory calculations. Beyond the lowest charge-transfer state, of which the energy can be determined with simple electrostatic models that we validate, the Bethe-Salpeter approach provides the full excitation spectrum. We evidence the existence of hot electron-hole states which are resonant in energy with the lowest donor intramolecular excitation and show an hybrid intramolecular and charge-transfer character, favouring the transition towards charge separation. These findings support the recently proposed scenario for charge separation at donor-acceptor interfaces through delocalized hot charge-transfer states.