Photo and electroluminescence from terbium doped zinc sulfide films deposited by spray pyrolysis

Undoped, silver doped and silver-terbium doped zinc sulfide photoluminescen t thin films have been prepared by the spray pyrolysis technique. The cryst alline structure of the deposited films is hexagonal wurzite, in all cases. The films have a preferential growth with the (0 0 2) direction perpendicu lar to the surface of the substrate. In general, the relative chemical comp ositions show that the films are formed by a zinc rich ZnS material. The ph otoluminescent excitation measurements are in agreement with the optical tr ansmission results indicating that the excitation mechanism is related to e lectron-hole pair generation across the ZnS band gap. The photoluminescent spectra show the typical bands associated with the transition from the D-5( 4) level to the F-7(6), F-7(5), F-7(4) and F-7(3) levels of the Tb3+ ions. The emission spectra for the undoped and silver doped films show the well k nown self-activated emission, centered at 460 and 490 nm, respectively. The dependence of the emission intensity on the temperature shows an energy ac tivation of 0.1 eV for competitive non-radiative transitions. Electrolumine scent devices using silver-terbium doped zinc sulfide films as active layer show emission spectra similar to those observed in photoluminescence measu rements but with a reduced intensity.