Epitaxial Strain Engineering of Monoclinic Bismuth Vanadate: A Path to Tailoring Optoelectronic and Photoelectrochemical Properties

Epitaxial strain engineering is a powerful tool to perturb the electronic structure of metal oxide photoabsorbers and to potentially improve its performance [1]. Little is known, however, as to the effects of epitaxial strain on monoclinic bismuth vanadate (m-BiVO₄), a transition metal oxide relevant to solar-to-fuels application. In this work, we contribute to the understanding on how epitaxial strain alters the BiVO₄ monoclinic lattice and the optoelectronic and photoelectrochemical properties of m-BiVO₄. We also reveal how the hydrostatic and deviatoric components of the strain tensor correlates with these properties. Epitaxial films of m-BiVO₄ deposited directly on yttrium-stabilized zirconia (YSZ) experiences volume-preserving deviatoric strains that modulate its Tauc bandgaps and polaronic photoluminescence emission [2]. Hydrostatic strains, on the other hand, seem to be more important for epitaxial BiVO₄ films deposited on more device-relevant indium tin oxide (ITO)/YSZ. For these fully epitaxial BiVO₄/ITO/YSZ films, compressive hydrostatic strains narrow the Tauc bandgaps and enhances the internal quantum efficiencies [3]. Epitaxial strain can thus be exploited to modulate the optoelectronic and PEC properties of BiVO₄.<br/>[1] B. Yildiz, “Stretching” the energy landscape of oxides—Effects on electrocatalysis and diffusion, MRS Bulletin, 39 (2014) 147.<br/>[2] E.N. Fernandez, D.A. Grave, R. van de Krol, F.F. Abdi, Strain-Induced Distortions Modulate the Optoelectronic Properties of Epitaxial BiVO₄Films, Advanced Energy Materials, 13 (2023) 2301075.<br/>[3] E.N. Fernandez, D.A. Grave, F.F. Abdi, R. van de Krol, <i>in preparation.</i>