Modelling the photochrome-TiO2 interface with Bethe-Salpeter and TD-DFT methods

TL;DR

This paper compares Bethe-Salpeter and TD-DFT methods for modeling the electronic excited states of photochromic molecules adsorbed on TiO2, highlighting the importance of method choice for accurate interface characterization.

Contribution

First application of Bethe-Salpeter approach to hybrid organic/inorganic TiO2 systems, evaluating and contrasting it with TD-DFT for interface excited-state modeling.

Findings

Bethe-Salpeter provides more accurate excited-state descriptions.

TD-DFT results vary significantly with exchange-correlation functionals.

Method choice critically affects interpretation of hybrid interface properties.

Abstract

Hybrid organic/inorganic-semiconductor systems have important applications in both molecular electronics and in photo-responsive materials. The characterization of the interface and of the electronic excited-states of these hybrid systems remains a challenge for state-of-the-art computational methods, as the systems of interest are large. In the present investigation, we present for the first time a many-body Green's function Bethe-Salpeter investigation of a series of photochromic molecules adsorbed onto TiO2 nanoclusters. Based on these studies, the performance of TD-DFT is assessed. Using a state-of-the-art computational protocol, the photochromic properties of different hybrid systems are assessed. This work shows that qualitatively different conclusions can be reached with TD-DFT relying on various exchange-correlation functionals for such organic/inorganic interfaces, and paves the way to more accurate simulation of many materials.