LaTiO2N crystallographic orientation control significantly increases visible-light induced charge extraction

Abstract

Photocharge extraction in the visible-light energy range is essential to sustain efficient photoelectrochemical processes driven by solar irradiation of photoanode materials. Recent literature has shown that crystallographic orientation can have a significant impact on the extraction of photocharges, though the difficulty of discriminating bulk and surface orientation effects on charge extraction often complicates any understanding as to the role each orientation may play. Our catalyst-decorated thin-film model system allows us to cleanly separate charge extraction limiting effects of bulk vs. surface orientation. As a result, our study reveals an anisotropic visible-light induced photocharge extraction dependence on the bulk crystallographic orientation in LaTiO₂N (LTON) photoanodes. In particular, the visible-light induced photocharge extraction is 30% higher for (011) films than (001) oriented thin films. Computational analysis of the LTON band diagram suggests that this is due to a higher potential energy and photocharge mobility along the (011) direction.