An investigation on photoluminescence and AC powder electroluminescence of ZnS:Cu,Cl,Mn,Te phosphor
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Hong Seok Seo, Joon Tae Ahn, and Jung Ho Song Basic Research Laboratory, Electronics and Telecommunications Research Institute, Daejeon 305-600, Republic of Korea
Woon Jin Chung Division of Advanced Materials Engineering, Kongju National University, Cheonan 22-717, Republic of Korea
Duk Young Jeona) Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea (Received 19 May 2011; accepted 4 August 2011)
ZnS:Cu,Cl,Mn,Te, which shows red AC powder electroluminescence (ACPEL) emission, was synthesized using a conventional wet synthesis and a sealed vessel method. The photoluminescence (PL) and ACPEL were characterized. After the second firing, 0.5 wt% tellurium (Te)-doped ZnS: Cu,Cl,Mn,Te phosphor shows almost red PL emission from the 4T1–6A1 transition of Mn21 ions, which are affected by the Te. Extended x-ray absorption fine structure analysis on the Mn K edge proved that the substitution of sulfur (S) with Te changes the local crystal field of the Mn21 ions and shifts an orange emission (;588 nm) to a red emission (;650 nm). A red ACPEL emission is first shown in 0.5 wt%Te-doped ZnS:Cu,Cl,Mn,Te after the third firing phosphor even though its luminance is not very high. The origin of the ACPEL emission is assumed to be not a CuxS–ZnS p–n junction but a CuxTe–ZnS p–n junction. Raman spectra were characterized to support that the red ACPEL emission is probably attributed to a CuxTe–ZnS p–n junction.
I. INTRODUCTION
An AC powder electroluminescence (ACPEL) device is operated by applying a high electric field to phosphor. Since an ACPEL device can be made using a screenprinting method on a flexible substrate, it has been used as a backlight of mobile phones and personal digital assistants (PDAs) because of its flexibility, uniform light emission, and low power consumption.1 The basic ACPEL mechanism is explained by the trapping and recombination of electrons and holes. When a high electric field is applied, electrons and holes are formed by the p–n junction of n-type ZnS and p-CuxS. The injected electrons are trapped by shallow donor centers such as CuxS-related defects, and the injected holes are trapped by recombination centers such as Cl ions. When the field is changed, an emission is generated by the recombination of electrons and holes.2 Until now, ACPEL emission has been only shown in ZnS-based phosphors such as ZnS:Cu,Cl phosphor, a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.260 2394
J. Mater. Res., Vol. 26, No. 18, Sep 28, 2011
http://journals.cambridge.org
Downloaded: 11 Mar 2015
which shows blue-green emission depending on the concentration of Cu, and ZnS:Cu,Cl,Mn phosphor, which shows orange or white emission depending on the concentration of Mn and Cu.1,3 However, a red emission has yet to be reported. To overcome this problem, red photoluminescence (PL) phosphors such as CaS:Eu, Ca2Si5N8: Eu, Y2O2:Eu, and ZnS:Mn,Te have been used.4–7 Among them, ZnS:Mn,Te has been known as a phosphor
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