Insights into effect of dopant site and dopant concentration on structural, electronic and optical properties of GaNbO[formula omitted] and its implications on visible light photocatalytic behavior: An ab-initio study

Abstract

First principles electronic structure calculations were performed on pure and chalcogenide doped GaNbO4. Doping with isoelectronic S and Se at the O sites in GaNbO4 shows a dopant site driven anisotropy in the structural properties which affects its electronic, optical and photocatalytic behavior. Band gap reduction in GaNbO4 is more with Se than S and this reduction can be regulated via choice of dopant, dopant site and dopant concentration. GaNbO4 bears an optical absorption profile similarity with anatase TiO2 (a-TiO2). Besides directional anisotropy, dopant induced absorption in the visible regime displays a site driven anisotropy, which, has implications on the onset of absorption and absorption peak heights. The visible region absorption peaks can be modulated with changes in the dopant concentration. Se dopant at a lower concentration gives a broader visible regime absorption peak of similar peak height as of a higher concentration S dopant. Undoped GaNbO4 has valence band maxima and conduction band minima at similar energies as a-TiO2 and these band placements can be altered through choice of dopant element, dopant site and dopant concentration to tune the visible light photocatalytic performance. Our study shows that doped GaNbO4 has a stronger visible range absorption than doped a-TiO2.