Tuning Optical and Electrical Properties of Vanadium Oxide with Topochemical Reduction and Substitutional Tin

Lance Wheeler, Thanh Luan Phan, Michelle Smeaton, Swagata Acharya, Shruti Hariyani, Marlena Alexander, Miranda Gonzalez, Elisa Miller, David Mulder, Sarbajit Banerjee, Katherine Jungjohann, Andrew Ferguson, Jeffrey Blackburn

Research output: Contribution to journalArticlepeer-review

Abstract

Vanadium oxides are widely tunable materials, with many thermodynamically stable phases suitable for applications spanning catalysis to neuromorphic computing. The stability of vanadium in a range of oxidation states enables mixed-valence polymorphs of kinetically accessible metastable materials. Low-temperature synthetic routes to, and the properties of, these metastable materials are poorly understood and may unlock new optoelectronic and magnetic functionalities for expanded applications. In this work, we demonstrate topochemical reduction of ..alpha..-V2O5 to produce metastable vanadium oxide phases with tunable oxygen vacancies (>6%) and simultaneous substitutional tin incorporation (>3.5%). The chemistry is carried out at low temperature (65 degrees C) with solution-phase SnCl2, where Sn2+ is oxidized to Sn4+ as V5+ sites are reduced to V4+ during oxygen vacancy formation. Despite high oxygen vacancy and tin concentrations, the transformations are topochemical in that the symmetry of the parent crystal remains intact, although the unit cell expands. Band structure calculations show that these vacancies contribute electrons to the lattice, whereas substitutional tin contributes holes, yielding a compensation doping effect and control over the electronic properties. The SnCl2 redox chemistry is effective on both solution-processed V2O5 nanoparticle inks and mesoporous films cast from untreated inks, enabling versatile routes toward functional films with tunable optical and electronic properties. The electrical conductance rises concomitantly with the SnCl2 concentration and treatment time, indicating a net increase in density of free electrons in the host lattice. This work provides a valuable demonstration of kinetic tailoring of electronic properties of vanadium-oxygen systems through top-down chemical manipulation from known thermodynamic phases.
Original languageAmerican English
Pages (from-to)10483-10495
Number of pages13
JournalChemistry of Materials
Volume36
Issue number21
DOIs
StatePublished - 2024

NREL Publication Number

  • NREL/JA-5K00-90982

Keywords

  • defects in solids
  • electrical conductivity
  • lattices
  • nanoparticles
  • oxides

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