Mind the Interface Gap.  Exposing Hidden Interface Defects at the Epitaxial Heterostructure between CuO and Cu2O

Aleksandar Živković, Giuseppe Mallia, Helen E King, Nora H de Leeuw, Nicholas M Harrison

Research output: Contribution to journalArticleAcademicpeer-review


Well designed and optimized epitaxial heterostructures lie at the foundation of materials development for photovoltaic, photocatalytic, and photoelectrochemistry applications. Heterostructure materials offer tunable control over charge separation and transport at the same time preventing recombination of photogenerated excitations at the interface. Thus, it is of paramount importance that a detailed understanding is developed as the basis for further optimization strategies and design. Oxides of copper are nontoxic, low cost, abundant materials with a straightforward and stable manufacturing process. However, in individual applications, they suffer from inefficient charge transport of photogenerated carriers. Hence, in this work, we investigate the role of the interface between epitaxially aligned CuO and Cu 2O to explore the potential benefits of such an architecture for more efficient electron and hole transfer. The CuO/Cu 2O heterojunction nature, stability, bonding mechanism, interface dipole, electronic structure, and band bending were rationalized using hybrid density functional theory calculations. New electronic states are identified at the interface itself, which are originating neither from lattice mismatch nor strained Cu-O bonds. They form as a result of a change in coordination environment of CuO surface Cu 2+ cations and an electron transfer across the interface Cu 1+-O bond. The first process creates occupied defect-like electronic states above the valence band, while the second leaves hole states below the conduction band. These are constitutional to the interface and are highly likely to contribute to recombination effects competing with the improved charged separation from the suitable band bending and alignment and thus would limit the expected output photocurrent and photovoltage. Finally, a favorable effect of interstitial oxygen defects has been shown to allow for band gap tunability at the interface but only to the point of the integral geometrical contact limit of the heterostructure itself.

Original languageEnglish
Pages (from-to)56331-56343
Number of pages13
JournalACS applied materials & interfaces
Issue number50
Publication statusPublished - 21 Dec 2022


  • Cu2O
  • CuO
  • band alignment
  • density functional theory
  • epitaxial interface
  • heterostructure


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