Materials control and d.c. electroluminescence in ZnS:Mn, Cu, Cl powder phosphors

Abstract

The preparation and d.c. electroluminescent properties of two types of powder phosphor are described. The first type is prepared by a slurrying technique in which the activators are added to pre-fired ZnS powder (post activation), and the second type involves the addition of the activators during the precipitation of the ZnS (simultaneous activation). Both types may subsequently be copper coated to give high-brightness panels, which exhibit an electrochemical forming process. The measurement of absolute luminance and efficiency is described in detail and the relationships between the characteristics and the impurity additions are discussed. Quantum efficiencies of greater than unity have been observed on slurried phosphors, and a luminance in the 1000 ft lambert region has been achieved with simultaneously activated, copper-coated phosphors. Temperature experiments on slurried phosphors indicate a maximum efficiency at room temperature and a five-orders drop in luminance to 120°K. A description of the forming process includes the fabrication of a gap-cell device, and a mechanism involving copper diffusion is put forward. Preliminary deterioration experiments have shown a half life of 900 h at 10 ft lamberts for constant-voltage operation. Direct collision excitation of manganese centres is believed to be the dominant mechanism.

D-C Conduction and Electroluminescence in Dielectric-Embedded ZnS:Mn,Cu,Cl

“…The brightness for a given current was not as high as that reported by Vecht eta[. (6), but the voltage required to produce a given brightness was less. The electroluminescent cells prepared by Vecht et al (6), from phosphor simultaneously activated and copper-coated also exhibited lower luminance for a given current and higher luminance for given voltage than those prepared from post-activated powder, but these required a forming step after preparation.…”

“…(6), but the voltage required to produce a given brightness was less. The electroluminescent cells prepared by Vecht et al (6), from phosphor simultaneously activated and copper-coated also exhibited lower luminance for a given current and higher luminance for given voltage than those prepared from post-activated powder, but these required a forming step after preparation. In cells prepared in the present work, the current decreases slowly with time, as also does the luminescence.…”

“…Several workers (5)(6)(7)(8)(9)(10)(11)(12)(13)(14) have investigated the absorption of metal cations onto silicon, germanium, and other semiconductor surfaces, usually using radio-* Electrochemical Society Active Member.…”

Some new display techniques-a critical survey

“…A sustained major commercial exploitation of liquid crystal displays seems probable. The d.c. electroluminescent [25][26][27] panel uses a zinc sulphide phosphor doped with manganese and copper, the 1 pm diameter particles being coated with a copper-rich conducting skin (Fig. l l).…”

White-electroluminescent device with ZnS:Mn, Cu, Cl phosphor

“…This EL is caused by the recombination of donor (Cu)-acceptor (Cl) pairs. The combination of Cu and Al (ZnS:Cu, Al) emits the green light at 550 nm, and the addition of Mn to Cu and Cl (ZnS:Mn, Cu, Cl) gives the yellow light at 590 nm [4,5].…”