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The additional (CH3NH3)2MnCl4 phase was observed upon increasing the Mn2+ dopant concentration, preventing the formation of Mn2+-doped CH3NH3PbCl3 NCs. We introduce an approach to avoid the formation of an impurity phase by switching the sequence for the addition of MnCl2 in the crystal growth process. [ABSTRACT FROM AUTHOR]

The additional (CH3NH3)2MnCl4 phase was observed upon increasing the Mn2+ dopant concentration, preventing the formation of Mn2+-doped CH3NH3PbCl3 NCs. We introduce an approach to avoid the formation of an impurity phase by switching the sequence for the addition of MnCl2 in the crystal growth process. [ABSTRACT FROM AUTHOR]

Organometal halide perovskites become important in the photovoltaic and light emitting devices due to the compositional flexibility with AMX3 formula (A is a monovalent organic ammonium cation; M is a metal ion; X is a halogen atom), imposing a significant demand to develop a synthetic route toward new types of nanocrystals. Although chemical pathways for perovskites nanoparticles were developed on the basis of the reprecipitation method, poor control of the nucleation and growth process results in a large size polydispersity that induces the ambiguities associated with a quantum confinement effect depending on their size. Here, a modified reprecipitation method is presented for the synthesis of CH3NH3PbBr3 perovskite nanoparticles with a controlled nanoparticle size by systematically tuning the feed ratio of the precursors. Fine control of the nanocrystal size provides new insights into the quantum confinement effect observed in microscale and nanoscale perovskite materials, where their energy bandgap is associated with the thickness of nanoparticles and invariant to preferential growth in a lateral dimension. [ABSTRACT FROM AUTHOR]

Sr2Si5N8:Eu2+ red-emitting nitridosilicate phosphor was prepared by a low temperature modified solid-state metathesis (MSSM) approach. The method is based on the nitridation of strontium chloride in presence of silicon and lithium nitrides. Lithium nitride was used as a solid source of nitrogen and as reduction agent for strontium chloride. We revealed that the formation of Sr2Si5N8 occurs via solid+liquid mechanism through intermediate SrSiN2 phase and found that Sr2Si5N8:Eu2+ can be synthesized by MSSM approach starting at a considerably low temperature (1100°C). We first showed the possibilities of using flux materials during the synthesis of complex alkaline earth-based nitridosilicates. The phosphor particles synthesized at optimized condition (1300°C and 6 hours) show a rod-like morphology in 1-5 μm width and 5-10 μm length. The color coordinate (CIE) of Sr2Si5N8:Eu2+ (2 wt%) are (0.6382; 0.3612) and emission spectrum exhibits a broad-band peaking at 628 nm. The synthesized phosphor was applied to LED package and white light has been obtained with CCT ∼ 4700 K and Ra ∼ 90-92 depending on driving current. The MSSM method has proven to be a cost-effective and facile way to prepare nitridosilicate phosphor with outstanding performance. An approximate chemical pathway for Sr2Si5N8:Eu2+ formation is proposed. [ABSTRACT FROM AUTHOR]

Abstract: In this research, CuInS2 quantum dots (QDs) have been studied as an excellent red emitting source for white LED because of its non-toxic deep red emission, and large Stokes shift properties. The CuInS2 QDs are synthesized by the one-pot method, which is a candidate for the mass-production method. In addition, formation of ZnS shells on QD surfaces has been conducted in order to reduce non-radiative recombination on its surface defects. The photoluminescence (PL) characteristics of core/shell quantum dot show that the maximum PL wavelength blue-shifts by about 80nm on increasing its intensity more than 6 times. Quantum yield (QY) of the CuInS2/ZnS QDs shows about 67% as the maximum value. The dispersion of the quantum dots in polystyrene, which is hydrophobic and transparent, was also conducted using co-dispersing toluene. Finally, the polystyrene/quantum dot composite was applied on blue LEDs and it showed luminous efficacy of 10.7lm/W and (0.4338, 0.1827) CIE coordinates. [Copyright &y& Elsevier]

The additional (CH 3 NH 3 ) 2 MnCl 4 phase was observed upon increasing the Mn 2+ dopant concentration, preventing the formation of Mn 2+ -doped CH 3 NH 3 PbCl 3 NCs. We introduce an approach to avoid the formation of an impurity phase by switching the sequence for the addition of MnCl 2 in the crystal growth process.