Effects of point vacancy and interstitial H on the carrier activity, separation, and absorption spectrum of ZnO: Li/Na/K

Abstract

The accurate understanding of Li/Na/K doping and point vacancies in ZnO is difficult. The interstitial H is also neglected in ZnO. In this paper, the generalized gradient approximation plane wave ultrasoft pseudopotential + U method is adopted based on the spin density functional theory to solve the abovementioned problem. The First-principles method is utilized to study the point vacancies and interstitial H on ZnO: Li/Na/K carrier activity, separation, and absorption spectrum. The formation energy of the Zn35MHiO35 (M: Li/Na/K) system is a large positive value regardless of the O- and Zn-rich conditions, indicating the difficulty of Zn35MHiO35 (M: Li/Na/K) system's formation and its poor stability. Compared with the same doping system, the Zn34MHiO36 (M: Li/Na/K) system exhibits smaller formation energy under O-rich conditions and is more stable. The formation energies of different doping systems under O- or Zn-rich conditions are in the following order: Zn35NaHiO35＜Zn35KHiO35＜Zn35LiHiO35. Zn35NaHiO35 and Zn35KHiO35 have negative formation energy and good stability. According to the analysis of the electric dipole moment, effective mass, and absorption spectrum, Zn35NaHiO35 can be separated easily and has the strongest carrier activity, the best absorption spectrum intensity, and the best red shift. These features are relatively advantageous in designing and preparing novel ZnO photocatalysts.