Effect of the Pr3+→Gd3+Pr^{3+} → Gd^{3+} energy transfer in multicomponent garnet single crystal scintillators

Luminescence processes in the undoped and Pr3+-doped (Gd,RE)3(Ga,Al)5O12, RE = Lu,Y, multicomponent garnets are studied by time-resolved photoluminescence spectroscopy. Energy transfer processes between Pr3+ and Gd3+ causing significant deterioration of the scintillation performance are considered in detail. As is shown in current work, an overlap of the 5d1–3H4 emission transition of Pr3+ and 8S–6Px absorption transition of Gd3+ results in unwanted depletion of Pr3+ 5d1 excited state and is further intensified by the concentration quenching in the Gd3+-sublattice. This process explains a drastic decrease of light yield in Pr3+-doped Gd3+-containing multicomponent garnets observed in a previous work

Growth and luminescent properties of (Lu−Y)AlO3(Lu-Y)AlO_{3}:Ce single crystalline films

The work is dedicated to the development of scintillating screens based on single crystalline films (SCF) of Ce doped Lu–Y–Al perovskites grown by the liquid phase epitaxy method. We show in this work that Lu1−xYxAP:Ce SCF with very good structural and optical perfection can be grown from the PbO-based flux onto YAP substrates in all range of x-values. We also found the Lu1−xYxAP:Ce SCF can be crystallized by LPE method from the lead free BaO–B2O3–BaF2 flux onto YAP substrates in the range of x values up to 0.4 formula units

Temperature dependence of the optical absorption coefficient of microcrystalline silicon

The optical absorption coefficient of amorphous and microcrystalline silicon was determined in a spectral range 400-3100 nm and a temperature range 77-350 K. Transmittance measurement and Fourier transform photocurrent spectroscopy were used. The measured data served as an input for our optical model of amorphous/microcrystalline tandem solar cell. Differences in the current generated in the amorphous and microcrystalline parts were computed, for an operating temperature between -20°C and +80°C. Optical spectra of microcrystalline silicon were compared to the spectrum of silicon on sapphire (without hydrogen and hydrogenated) and the observed difference was interpreted in terms of a different density of defects and higher disorder of microcrystalline Si. © 2004 Elsevier B.V. All rights reserved

Bi3+−Pr3+Bi^{3+}-Pr^{3+} energy transfer processes and luminescent properties of LuAG:Bi,Pr and YAG:Bi,Pr single crystalline films

Absorption, cathodoluminescence, excitation spectra of photoluminescence (PL) and PL decay kinetics were studied at 300 K for the double doped with Bi3+–Pr3+ and separately doped with Bi3+ and Pr3+ Lu3Al5O12 (LuAG) and Y3Al5O12 (YAG) single crystalline film (SCF) phosphors grown by the liquid phase epitaxy method. The emission bands in the UV range arising from the intrinsic radiative transitions of Bi3+ based centers, and emission bands in the visible range, related to the luminescence of excitons localized around Bi3+ based centers, were identified both in Bi–Pr and Bi-doped LuAG and YAG SCFs. The energy transfer processes from the host lattice simultaneously to Bi3+ and Pr3+ ions and from Bi3+ to Pr3+ ions were investigated. Competition between Pr3+ and Bi3+ ions in the energy transfer processes from the LuAG and YAG hosts was evidenced. The strong decrease of the intensity of Pr3+ luminescence both in LuAG:Pr and YAG:Pr SCFs phosphors, grown from Bi2O3 flux, is observed due to the quenching influence of Bi3+ flux related impurity. Due to overlap of the UV emission band of Bi3+ centers with the f–d absorption bands of Pr3+ ions in the UV range and the luminescence of excitons localized around Bi ions with the f–f absorption bands of Pr3+ ions in the visible range, an effective energy transfer from Bi3+ ions to Pr3+ ions takes place in LuAG:Bi,Pr and YAG:Bi,Pr SCFs, resulting in the appearance of slower component in the decay kinetics of the Pr3+ d–f luminescence