Structural and optical investigation of (V, Al) doped and co-doped ZnO nanopowders: Tailored visible luminescence for white light emitting diodes

This paper deals with co-precipitation synthesis and characterization of undoped, Al, V doped, and (Al + V) co-doped ZnO nanopowders. Complementary techniques are used: X-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance and photoluminescence (PL) spectroscopies. XRD analysis revealed the formation of hexagonal-wurtzite structure for all samples. The average crystallite size decreases from 40 to 20 nm by doping ZnO NPs. TEM images showed quasi-spherical shaped nanoparticles. The UV-visible absorption spectra revealed that doping and co-doping induce slight red-shift of gap energy (3.29eV-3.27eV). The Urbach energy increases mainly with V doping, suggesting an increase in disorder and defects levels. PL spectra exhibit narrow and wide emissions in UV and visible regions respectively. Gaussian deconvolution of the broad visible peaks revealed several overlapped emissions. Mainly V incorporation in ZnO (single and double doping) notably improves visible luminescence. It leads to widening of the visible emission from 460 to 585 nm.