Many-body Green's function study of coumarins for dye-sensitized solar cells

TL;DR

This study employs many-body Green's function methods to accurately compute excitation energies of coumarin dyes, which are promising alternatives to traditional dyes in solar cells, demonstrating the effectiveness of these approaches for charge-transfer systems.

Contribution

It demonstrates that GW and Bethe-Salpeter methods can accurately predict excitation energies of coumarin dyes without adjustable parameters, advancing computational design of solar cell materials.

Findings

Charge-transfer excitation energies match reference calculations.

GW and Bethe-Salpeter methods accurately describe Frenkel and charge-transfer excitations.

Approaches are parameter-free and applicable to extended systems.

Abstract

We study within the many-body Green's function $GW$ and Bethe-Salpeter formalisms the excitation energies of several coumarin dyes proposed as an efficient alternative to ruthenium complexes for dye-sensitized solar cells. Due to their internal donor-acceptor structure, these chromophores present low-lying excitations showing a strong intramolecular charge-transfer character. We show that combining $GW$ and Bethe-Salpeter calculations leads to charge-transfer excitation energies and oscillator strengths in excellent agreement with reference range-separated functional studies or coupled-cluster calculations. The present results confirm the ability of this family of approaches to describe accurately Frenkel and charge-transfer photo-excitations in both extended and finite size systems without any system-dependent adjustable parameter, paving the way to the study of dye-sensitized semiconducting surfaces.