Origin of a large difference of power conversion efficiency between the hexagonal LuMnO3 and the hexagonal LuFeO3 ferroelectric photovoltaics

• Published in: Materials chemistry and physics Vol. 263; p. 124344
• Main Authors: Brito, D.M.S., Melo, A.T., Lima, A.F., Lalic, M.V.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.04.2021; Elsevier BV
• Subjects: Anisotropy; Basal plane; Density functional theory; DFT calculations; Effective mass; Electricity distribution; Electronic structure; Energy conversion efficiency; Excitons; Ferroelectric materials; Ferroelectric photovoltaics; Ferroelectricity; First principles; Holes (electron deficiencies); Photoelectric effect; Photoelectric emission; Photovoltaic cells; Ferroelectric photovoltaics; Electronic structure; Effective mass; DFT calculations
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2021.124344

Hexagonal LuMnO3 (h-LMO) and LuFeO3 (h-LFO) compounds, in their ferroelectric phases (space group P63cm), are promising ferroelectric photovoltaic materials for converting sunlight into electricity. However, the recent experimental studies demonstrate that the h-LMO exhibits much higher solar to electric power conversion efficiency (PCE) than the h-LFO. In this study, we explain the origin of this difference, basing our analysis on the electronic structure of both compounds, determined from the first-principles calculations at the density functional theory level. Our results demonstrate that the h-LMO PCE is higher than the h-LFO PCE because of the two facts: (1) the effective mass of the photogenerated charges in the h-LFO is larger than in the h-LMO, (2) the binding energy of the photogenerated electron-hole pairs (excitons) is higher in the h-LFO than in the h-LFO. We also report a high anisotropy of the electronic photocurrent in both compounds: due to much larger electron effective mass along the c-axis direction, the photocurrent flow along any direction within the hexagonal basal plane is much more efficient. •Ferroelectric photovoltaics LuMnO3 and LuFeO3 were considered.•Large difference in power conversion efficiency (PCE) between them was investigated.•Higher PCE of LuMnO3 is due to smaller effective masses of photocarriers.•Higher PCE of LuMnO3 is due to lower binding energy of photo-generated excitons.•In both compounds, the photocurrent flow is highly anisotropic.