Determining the Conduction Band-Edge Potential of Solar-Cell-Relevant Nb2O5 Fabricated by Atomic Layer Deposition

William L. Hoffeditz, Michael J. Pellin, Omar K. Farha, Joseph T. Hupp

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Often key to boosting photovoltages in photoelectrochemical and related solar-energy-conversion devices is the preferential slowing of rates of charge recombination - especially recombination at semiconductor/solution, semiconductor/polymer, or semiconductor/perovskite interfaces. In devices featuring TiO2 as the semiconducting component, a common approach to slowing recombination is to install an ultrathin metal oxide barrier layer or trap-passivating layer atop the semiconductor, with the needed layer often being formed via atomic layer deposition (ALD). A particularly promising barrier layer material is Nb2O5. Its conduction-band-edge potential ECB is low enough that charge injection from an adsorbed molecular, polymeric, or solid-state light absorber and into the semiconductor can still occur, but high enough that charge recombination is inhibited. While a few measurements of ECB have been reported for conventionally synthesized, bulk Nb2O5, none have been described for ALD-fabricated versions. Here, we specifically determine the conduction-band-edge energy of ALD-fabricated Nb2O5 relative to that of TiO2. We find that, while the value for ALD-Nb2O5 is indeed higher than that for TiO2, the difference is less than anticipated based on measurements of conventionally synthesized Nb2O5 and is dependent on the thermal history of the material. The implications of the findings for optimization of competing interfacial rate processes, and therefore photovoltages, are briefly discussed.

Original languageEnglish
Pages (from-to)9298-9306
Number of pages9
JournalLangmuir
Volume33
Issue number37
DOIs
Publication statusPublished - Sep 19 2017

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ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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