Effect of annealing on the optical constants of ZnO nanowires for energy harvesting applications

The effect of annealing temperature on the optical constants of hydrothermally prepared ZnO nanowires was investigated for potential application in the fabrication of solar energy harvesting devices. Annealing at led to an increase in the visible region refractive index and decrease in the extinction coefficient, which both exhibited an opposite trend at. This was attributed to the initial increase in scattering and decrease in absorption of incident light at which then reversed its behaviour at,. The refractive index was around, while the extinction coefficient was around in the visible range. These values were relatively higher than those of the gallium and aluminium co-doped ZnO (GAZO) thin films used as seed layers, which gave rise to the relatively lower transmittances observed for the ZnO nanowires. Other optical constants such as the effective single oscillator energy, dispersion energy, static dielectric constant, static refractive index (and the nonlinear refractive index (were determined. The highest figure of merit of was determined at which demonstrated the significance of annealing in tailoring the optoelectronic properties of ZnO nanowires for application in solar energy harvesting device fabrication.