Effects of oxygen vacancy on the electronic structure and absorption spectra of bismuth oxychloride

In order to evaluate the effects of oxygen vacancy on the electronic structure and absorption spectra of bismuth oxychloride (BiOCl), the structural parameters, electronic structures, formation energies and absorption spectra of the perfect BiOCl and BiOCl containing oxygen vacancy (BiO15/16Cl) have been studied using first-principles method based on density functional theory. The simplified models for the possible formation mechanisms of oxygen vacancy, and the effective separation and lower recombination processes of photo-induced electron–hole pairs in BiO15/16Cl are built up and discussed. The calculated structural parameter error is less than 7.5%, showing that our approach is a suitable method. The calculated formation energies reveal that the existence of oxygen vacancy in BiOCl sample is very possible. The densities of states of BiO15/16Cl indicate that the oxygen vacancy would introduce a new electronic state in forbidden band compared with those of the perfect BiOCl, and this new electronic state could act as a capture center for excited electrons and, consequently, improve the effective separation of electron–hole pairs and be more beneficial for utilizing visible light. The absorption spectra show that BiO15/16Cl exhibits a new absorption peak at about 2.72 eV (456 nm) in the visible region, which is in good agreement with the experimental value of 468 nm.