Unraveling the influence of oxygen vacancy with and without replacement on Cu2O: A DFT Study

Abstract

This study delves into the structural and electronic effects of oxygen vacancies in Cu₂O using density functional theory (DFT) enhanced with Hubbard U corrections (DFT+U). A 3x2x1 supercell of Cu₂O was employed. The study meticulously investigates the removal of 1, 2, and 3 oxygen atoms, analyzing the ensuing changes in both structural stability and electronic properties, with particular emphasis on the band gap.The structural analysis revealed that oxygen vacancy formation induces significant modifications in Cu-O and Cu-Cu bond lengths, with elongations observed around the vacancy sites in which the Cu-Cu bond length decreased to 2.4035 Å, compared to 3.0066 Å in the pristine structure. The structural distortion followed the Jahn-Teller effect, leading to the formation of isolated units and transformation in bond angles. The introduction of oxygen vacancies without replacement (WOR) caused significant distortions in the Cu₂O lattice, which were more pronounced with increasing vacancy concentration. The Cu-O bond length increased from 1.8492 Å in the pristine structure to 1.9840 Å in the single vacancy configuration. However, in the oxygen vacancies with replacement (WR) the Cu-Cu bond length increased slightly to 3.0218 Å, with the Cu-O bond length expanding to 1.8505 Å. The band structure analysis indicated a decrease in the band gap with increasing vacancy concentration. The pristine Cu₂O exhibited a band gap of 1.67 eV as calculated, which was increased to 1.97 eV with a single vacancy and 1.16 eV with two vacancies, reflecting the significant impact of oxygen vacancies on the material’s optoelectronic properties. The findings underscore the critical role of oxygen vacancies in modulating the structural and electronic properties of Cu2O, providing insights that are pivotal for optimizing its performance in applications like photocatalysis and solar cells.