Quasiparticle level alignment for photocatalytic interfaces

TL;DR

This paper systematically compares various many-body electronic structure methods to accurately determine level alignment at photocatalytic interfaces, crucial for understanding and improving photocatalytic activity.

Contribution

It demonstrates that $G_0W_0$ and a new $ ext{scQP}GW_1$ approach are essential for accurate interfacial level alignment, setting a new standard for interpreting experimental spectra.

Findings

$G_0W_0$ and $ ext{scQP}GW_1$ accurately reproduce experimental level alignments.

Standard DFT methods fail to predict correct interfacial levels.

The study provides a benchmark for future theoretical investigations of photocatalytic interfaces.

Abstract

Electronic level alignment at the interface between an adsorbed molecular layer and a semiconducting substrate determines the activity and efficiency of many photocatalytic materials. Standard density functional theory (DFT) based methods have proven unable to provide a quantitative description of this level alignment. This requires a proper treatment of the anisotropic screening, necessitating the use of quasiparticle (QP) techniques. However, the computational complexity of QP algorithms has meant a quantitative description of interfacial levels has remained elusive. We provide a systematic study of a prototypical interface, bare and methanol covered rutile TiO$_2$(110) surfaces, to determine the type of many-body theory required to obtain an accurate description of the level alignment. This is accomplished via a direct comparison with metastable impact electron spectroscopy (MIES), ultraviolet photoelectron spectroscopy (UPS) and two-photon photoemission (2PP) spectra. We consider GGA DFT, hybrid DFT and $G_0W_0$, $\mathrm{scQP}GW1$, $\mathrm{scQP}GW_0$, and $\mathrm{scQP}GW$ QP calculations. Our results demonstrate that $G_0W_0$, or our recently introduced $\mathrm{scQP}GW1$ approach, are required to obtain the correct alignment of both highest occupied and lowest unoccupied interfacial molecular levels (HOMO/LUMO). These calculations set a new standard in the interpretation of electronic structure probe experiments of complex organic molecule-semiconductor interfaces.