Bulk photovoltaic effect in hexagonal LuMnO3 single crystals

Open Access

Abstract

Hexagonal manganites, such as h-LuMnO3, are ferroelectric and have a narrow electronic band gap of ≈1.5eV. Here we report on the photoresponse of h-LuMnO3 single crystals. It is found that the short circuit photocurrent density (Jsc) and the open circuit voltage (Voc) are dependent on the direction of the polarization plane of a linearly polarized impinging light. Its angular dependence indicates the contribution of bulk photovoltaic effect to the short circuit photocurrent. It is also observed that a switchable drift photocurrent, originating from the depoling field of the ferroelectric and thus tunable (<10%) by its polarization direction, also contributes to Jsc. Although its presence precludes accurate determination of the bulk photovoltaic tensor elements and Glass coefficients, some bounds can be established. The Glass coefficients are found to be significantly larger than those obtained in BiFeO3. We argue that the smaller band gap of h-LuMnO3, its distinctive bipyramidal crystal field, and electronic configuration (3d4 vs 3d5), account for the difference and suggest a path towards ferroelectrics of higher photoconversion efficiency. ; Financial support from the Spanish Ministry of Science, Innovation and Universities, through the "Severo Ochoa" Programme for Centers of Excellence in R&D (FUNFUTURE CEX2019-000917-S), PID2020-118479RBI00 (AEI/FEDER, EU) (AEI/FEDER, EU), and PID2019- 107727RB-I00 (AEI/FEDER, EU) projects, and from Generalitat de Catalunya (2017 SGR 1377) is acknowledged. I.F. acknowledges RyC Contract RYC-2017-22531. Project supported by a 2020 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation. The theoretical component of this work (A.M.S. and A.M.R.) was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award No. DE-FG02-07ER46431. Computational support was provided by the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy, Office of Science User Facility located at Lawrence Berkeley National Laboratory, operated under Contract No. DE-AC02- 05CH11231.The experimental and theoretical contributions of Y.S. are financially supported by China Scholarship Council (CSC), respectively with No. 201806410010. The work of Y.S. has been done as a part of her Ph.D. program in Materials Science at Universitat Autònoma de Barcelona. ; With funding from the Spanish government through the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019-000917-S). ; Peer reviewed