ZnO:Al – A yellowish orange emitting phosphor for Blue Light -Converted White Light Emitting Diode (WLEDs)

Abstract

Al-doped ZnO, which emits a yellowish orange light at the excitation of blue light, is prepared by means of a sol-gel combustion method, using zinc acetate, aluminium nitrate, and urea as precursors. XRD analysis reveals that the obtained material shows hexagonal wurtzite structure of ZnO. This phosphor material is excitable in a wide range of wavelength from 350 to 500 nm with an excitation maximum at 470 nm. The concentration of Al varies from 5 mol% to 15 mol% with respect to Zn and a maximum photo-luminescent emission intensity is obtained at 15 mol%. At 455 nm excitation, Al-doped ZnO shows a broad band yellowish orange emission starting from 470 to 620 nm with an emission maximum at 530 nm. At a blue LED excitation, it emits a warm white light with a CRI of 91 and CIE color co-ordinates of (x = 0.50, y = 0.39). This Al-doped ZnO can be used as a blue light converted yellowish- orange emitting phosphor material for applications in WLEDs.