Effect of intrinsic point defects on ZnO electronic structure and absorption spectra

The effect of intrinsic point defects on the electronic structure and absorption spectra of ZnO was investigated by first-principle calculation. Among the intrinsic point defects in ZnO, oxygen vacancies (V-O) and interstitial zinc (Zn-i) have the lower formation energy and the more stable structure under zinc(Zn)-rich condition, whereas zinc vacancies (V-zn) and interstitial oxygen (O-i) have the lower formation energy and the more stable structure under oxygen(O)-rich condition. The band gap of Zn36ZniO36 becomes narrow and the absorption spectrum has a redshift. In the visible region, the photo-excited electron transition of Zn36O35 is graded from the valence band top to the impurity level and then to the conduction band bottom, showing the redshift of absorption spectrum of Zn36O35 and explaining the reason of V(O )forming a deep impurity levels in ZnO. Moreover, the impurity energy level of Zn36O35 coincides with the Fermi level, indicating the significant trap effect and the slow recombination of electrons and holes, which are conducive to the design and preparation of novel ZnO photocatalysts. The band gap of Zn35O36 and Zn36OiO36 broadened and the absorption spectrum showed blueshift, explaining the different values of the ZnO band gap width.