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We report the optical properties and morphological structure of potential green phosphors ͑Sr 1−x Ca x Ga 2 S 4 :Eu, x = 0.0-1.0͒ for application in phosphor-converted three-band white light emitting diodes ͑LEDs͒. A series of Sr 1−x Ca x Ga 2 S 4 :Eu phosphors was synthesized using NaBr-aided solid-state reactions in a flowing H 2 S stream. They all crystallized with the orthorhombic PbGa 2 Se 4 phase, and their emissions were efficiently excited up to 480 nm. The optical and morphological suitability of Sr 1−x Ca x Ga 2 S 4 :Eu phosphors is discussed in terms of their application as coatings for altering the color of blue LEDs.

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We determined the effects of varying the structural parameters of two-dimensional (2D) square lattice SiO2 photonic crystal (PC) arrays on the efficiency of extraction of the photoluminescence (PL) of sputter-deposited Y2O3:Eu3+ thin films, in which the interface between the phosphor layer and the quartz substrate was modified with the 2D SiO2 PC pattern. The structural parameters of the 2D PC pattern were optimized according to their effects on the light extraction efficiency and similar trends were found for both the as-grown and the post-annealed samples; the samples with lattice constants in the range 400−600 nm exhibit the largest enhancement, there is increased enhancement with pattern height increases up to ∼420 nm, and the samples with a filling ratio of ∼0.20 exhibit the maximum enhancement of the extraction efficiency. For 2D PC patterns with a depth of 420 nm, a lattice constant of 600 nm, and a filling ratio of 0.2, the optimum PL extraction efficiencies of as-grown (350 °C) and post-annealed (900 °C) Y2O3:Eu3+ thin-film phosphors were improved by factors of more than 8.6 and 4.8, respectively, with respect to those of flat Y2O3:Eu3+ thin films. We investigated the reasons for this difference between the enhancements of the extraction efficiencies of the as-grown and post-annealed Y2O3:Eu3+ thin films deposited on 2D PC quartz substrates, in order to determine the factors affecting the extraction efficiencies of 2D PC layer assisted thin-film phosphors.

This study examined the effects of the thickness of Y(2)O(3):Eu(3+) phosphor films on quartz substrates coated with two-dimensional (2D) SiO(2) square-lattice nanorod photonic crystal layers (PCL) at identical heights on their extraction and absorption efficiency. The photoluminescence (PL) efficiency enhancement ratio decreased exponentially with increasing Y(2)O(3):Eu(3+) film thickness. The 2D PCL-assisted Y(2)O(3):Eu(3+) film with a thickness (t) = 400 nm showed enhancement in the upward and downward PL emission by factors of 6.2 and 8.6, respectively, with respect to those of a conventional flat film. This observation was attributed to diffraction scattering of the excitation and emission light.