Electroluminescence of Devices with Thin-Film CaS:Ce³⁺, Cl^- as the Active Luminescent Layer

Abstract

Thin-film CaS:Ce3+, Cl- has been successfully employed for the first time as the active layer of an a.c. thin-film electroluminescent device. In order to compare the performance of a device using this material with that of devices employing the usual ZnS:Mn2+ material, MISM (metal-insulator-semiconductor-metal), ISM, and MSM devices were fabricated. Of these three devices, the singly-insulated device had the highest brightness, of 100 cd/m2, at a frequency of 5 kHz and a pulse height of 200 V. The brightness of this device is still lower than that of devices employing the usual ZnS:Mn2+. This is attributed to the smaller number of internal carriers and the smaller amount of carrier accumulation in the vicinity of the interface between the active luminescent layer and the insulating layer.

Doping-Mediated Size and Structure Tailoring of CaS Nanocrystals

“…Typically, the aliovalent doping can induce the formation of interstitial S 2– or Ca 2+ vacancy to make up for the extra positive charge. − We speculate that the dark Ce was associated with interstitial S 2– . The S-rich environment places the Ce 3+ absorption through the 4f → 5d transition in the green spectrum region, resembling the coloration effect of γ-Ce 2 S 3 . − …”

Solid solubility limit of cerium in CaS: Ce3+ phosphor

“…Now there is one more problem that must be solved before device applications, namely, the solid solubility limit of cerium in CaS host. Without a definite knowledge of the solid solubility limit of cerium in CaS host, it is hard to reproduce the colour of CaS : C e 3+ phosphor emission, This complication has been pointed out by Ogawa et al [6] in their recent studies of CaS : Ce 3+ .…”