Using G0W0 Level Alignment to Identify Catechol’s Structure on TiO2(110)

Abstract

We perform state-of-the-art calculations for a prototypical dye sensitized solar cell: catechol on rutile TiO2(110). Catechol is often used as an anchoring group for larger more complex organic and inorganic dyes on TiO2 and forms type II heterojunctions on TiO2(110). In particular, we compare quasiparticle (QP) G0W0 with hybrid exchange correlation functional (HSE) density functional theory (DFT) calculations for the catechol–rutile TiO2(110) interface. In so doing, we provide a theoretical interpretation of ultraviolet photoemission spectroscopy (UPS) and inverse photoemission spectroscopy (IPES) experiments for this prototypical system. Specifically, we demonstrate that the position, presence, and intensity of peaks associated with catechol’s HOMO, intermolecular OH–O bonds, and interfacial hydrogen bonds to the surface bridging O atoms (ObrH–C and ObrH–O) may be used to fingerprint deprotonation of catechol’s OH anchoring groups. Furthermore, our results suggest deprotonation of these groups, while being nearly isoenergetic at high coverages, may significantly increase the photovoltaic efficiency of catechol–TiO2(110) interfaces.