Luminescence of ZnWO4 and CdWO4 thin films prepared by spray pyrolysis

Thin films of ZnWO4 and CdWO4 were prepared by spray pyrolysis and the structural, optical, and luminescence properties were investigated. Both ZnWO4 and CdWO4 thin films showed a broad blue-green emission band. The broad band of ZnWO4 films was centered at 495 nm (2.51 eV) consisted of three bands at 444 nm (2.80 eV), 495 nm (2.51 eV) and 540 nm (2.30 eV). The broad band of CdWO4 films at 495 nm (2.51 eV) could be decomposed to three bands at 444 nm (2.80 eV), 495 nm (2.51 eV) and 545 nm (2.28 eV). These results are consistent with emission from the WO66− molecular complex. The luminance and efficiency for ZnWO4 film at 5 kV and 57 μA/cm2 were 48 cd/m2 and 0.22 lm/w, respectively, and for CdWO4 film the values were 420 cd/m2 and 1.9 lm/w.