Design of Semiconducting Tetrahedral Mn1-xZnxO Alloys and Their Application to Solar Water Splitting

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Abstract

Transition metal oxides play important roles as contact and electrode materials, but their use as active layers in solar energy conversion requires achieving semiconducting properties akin to those of conventional semiconductors like Si or GaAs. In particular, efficient bipolar carrier transport is a challenge in these materials. Based on the prediction that a tetrahedral polymorph of MnO should have such desirable semiconducting properties, and the possibility to overcome thermodynamic solubility limits by nonequilibrium thin-film growth, we exploit both structure-property and composition-structure relationships to design and realize novel wurtzite-structure Mn1-xZnxO alloys. At Zn compositions above x ≈ 0.3, thin films of these alloys assume the tetrahedral wurtzite structure instead of the octahedral rocksalt structure of MnO, thereby enabling semiconductor properties that are unique among transition metal oxides, i.e., a band gap within the visible spectrum, a band-transport mechanism for both electron and hole carriers, electron doping, and a band lineup suitable for solar hydrogen generation. A proof of principle is provided by initial photo-electrocatalytic device measurements, corroborating, in particular, the predicted favorable hole-transport properties of these alloys.

Original languageAmerican English
Article number021016
Number of pages13
JournalPhysical Review X
Volume5
Issue number2
DOIs
StatePublished - 2015

NREL Publication Number

  • NREL/JA-5K00-60832

Keywords

  • ab initio computation
  • materials design
  • non-equilibrium materials
  • semiconductor oxides

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