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Enhanced transition probabilities and trapping state emission of quencher impurities doped CaS:Mn phosphors

RAJESH SHARMA1,* , H. S. BHATTI2, KWANGSEUK KYHM1,*

Affiliation

  1. Research Center for Dielectric and Advanced Matter Physics, Department of Physics, Pusan National University, Busan 609-735, South-Korea
  2. Department of Physics, Punjabi University, Patiala-147 002, India

Abstract

We have synthesized singly (Mn) and doubly doped (Mn and quencher impurities X = Fe, Co and Ni) CaS phosphor samples using high temperature synthesis technique. Photoluminescence (PL) excitation spectra of these phosphors show peak around 264 nm due to band to band/defect level excitation while emission spectra show strong 585 nm emission peak which is due to incorporation of Mn impurity in host CaS phosphor. Adding the quencher impurities to CaS:Mn phosphors, no considerable change was observed in the emission spectra. The weak luminescence due to quencher impurities in CaS phosphors was suppressed by strong and broad band orange emission of Mn impurity, as the samples were doubly doped with Mn and quencher impurities. Enhancement of photoluminescence intensity of CaS:Mn:Co phosphors was reported in comparison to CaS:Mn:Ni or Fe phosphors at liquid nitrogen temperature. Although we observed no appreciable change in PL spectra of CaS:Mn phosphors co-doped with quencher impurities, ten-fold increase in the transition probabilities was noticed. A dynamic charge carrier relaxation model has been proposed to explain the observed abnormal behaviour of shallow and deep trap state emission from CaS:Mn, X doped phosphors..

Keywords

Trap-depth values, Quencher impurities, CaS:Mn phosphors, Radiative transition probabilities, Laser induced excitation.

Submitted at: July 5, 2008
Accepted at: Jan. 29, 2009

Citation

RAJESH SHARMA, H. S. BHATTI, KWANGSEUK KYHM, Enhanced transition probabilities and trapping state emission of quencher impurities doped CaS:Mn phosphors, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 1, pp. 62-69 (2009)