Electroluminescent ZnS–Cu films made by metal–organic chemical vapour deposition and thermodiffusion

Abstract

ZnS, ZnS–Cu films were deposited using an original chemical method under atmospheric pressure on to glass substrates to form thin-film electroluminescent (TFEL) devices. The ZnS, ZnS–Cu films were doped with Cu, Cl by a thermodiffusion (thermal diffusion) method from a ZnS powder doped with Cu and Cl. The TFEL devices had a conventional double insulating structure. The investigated TFEL devices had performance parameters including blue colour emission (λmax = 455 nm) and a brightness of 10 cd m−2 under sine wave excitation at a voltage of 60 V and a frequency of 5 kHz. The composition of the spectra was studied and from these results it was shown that the relative intensity of the bands and the maximum location are determined from the growth conditions. There are two main types of electroluminescent (EL) spectra, which differ in the number and location of green emission bands. A set of conditions was found for the fabrication of stable ZnS–Cu, Cl devices. The degradation behaviour of the ZnS–Cu, Cl device fabricated using the new method is the same as that of a commercial thin-film phosphor. The possibility of obtaining a stable ZnS–Cu emitter is shown. The EL mechanism and degradation characteristics are discussed.