Luminescence and Energy Transfer in Thin Films of SrGa2 S 4 : Ce

Abstract

Excitation and photoluminescence (PL) spectra of both nominally undoped and Ce3+‐activated SrGa2S4 thin films have been measured at various temperatures between 10 and 300 K. The undoped film shows a complex emission band which appears to involve emission from different defect states. Each defect center effects the recombination kinetics and luminescence spectra in a different temperature region. At 77 K, recombination is dominated by the highly associated defect centers producing an intense red emission band. At higher temperatures, thermalization effects reduce the net capture rates at the competitive defect centers, and recombination through the defect centers at room temperature produces a broad emission band with the peak in the blue spectral region. Evidence of the interaction and energy exchange between defect centers and Ce3+ activator states is inferred from the rise and decay time measurements of PL emission in SrGa2S4:normalCe thin films. As a result of thermalization, the efficiency of energy transfer to Ce3+ ions increases at room temperature but at the expense of introducing a long afterglow into the activator decay. Measurements of temperature dependence of PL intensity suggest that the kinetic model for energy transfer in SrGa2S4:normalCe combines aspects of long‐range resonance transfer and indirect thermalization from defect states with subsequent retrapping at the activator sites. In addition, possible mechanisms are discussed which may explain the observed concentration dependence of the Ce3+ fluorescence decay time. Preliminary results are reported for a thin‐film electroluminescent device with a SrGa2S4:normalCe , Li phosphor layer prepared by the low‐temperature deposition from binary vapors process. © 1999 The Electrochemical Society. All rights reserved.

Development of rare earth doped CaS phosphors for radiation detection

“…where IðtÞ is the intensity at t, I 0 is the intensity at t = 0, A 1 , A 2 , and A 3 are constants, and¸1,¸2, and¸3 are decay time constants. The decay time constants are shown in 37) and KLuS 2 :Ce single crystals (2.5 %, 30.1 and 88.5 ns) 38) and attributed to the 5d4f transition of Ce 3+ . The slower component may correspond to the excited state ionization, in which the electron escapes from the Ce 3+ 5d 1 excited state to the bottom of the conduction band and returns to the excited state of Ce 3+ and recombines with the hole at Ce 3+ .…”

Developments in Luminescence and Display Materials Over the Last 100 Years as Reflected in Electrochemical Society Publications

“…Both Mg and Cr have a favorable influence on the photoluminescent properties; Mg enhances the intensity of the green emission and Cr shortens the decay time. Djazovski et al 200 studied the excitation and emission spectra of nominally pure and Ce 3ϩ -activated SrGa 2 S 4 thin films. They reported preliminary results of a thin-film electroluminescent device with SrGa 2 S 4 : Ce, Li phosphor layer.…”

Thin film electroluminescent cells on the basis of Ce‐doped CaGa 2 S 4 and SrGa 2 S 4 prepared by flash evaporation method

“…There are various techniques (for example, molecular beam epitaxy [2], sputtering [1], deposition from binary vapours [3]) to prepare the CaGa 2 S 4 :Ce and SrGa 2 S 4 :Ce thin films. In our previous report [4], feasibility of thin film electroluminescence (TFEL) application of the films prepared by the flash evaporation method was shown on the basis of optical and X-ray characterizations of the films.…”