Bo Wang,Shan Zhang,Bin Liu,Jinkai Li,Bingqiang Cao,Zongming Liu
CsPbBr3 perovskite quantum dots (QDs) have attracted great attention due to their different photoluminescent and electronic properties. However, the toxicity and low stability hinder their practical application. Here, low-toxicity Sn-substituted cesium lead bromide perovskite QDs were synthesized via the room temperature crystallization method. A phase transition of the perovskite quantum dots with the concentration of Sn increasing was found: the crystal phase of CsPbBr3:Sn perovskite QDs starts to be transformed into Cs4PbBr6:Sn perovskite QDs when the SnBr2 precursor exceeds 30 at. %. In this process, the controlled-color emission of perovskite QDs from green to blue can be realized. To improve the stability of quantum dots, CsPbBr3:Sn@SiO2 and Cs4PbBr6:Sn@SiO2 were synthesized via a simple one-step synthesis with hydrolysis of tetramethoxysilane in toluene solution containing perovskite QDs. The results show that CsPbBr3:Sn@SiO2 and Cs4PbBr6:Sn@SiO2 exhibited higher water stability and water solubility than pure QDs. In a mixed solution of toluene and water, the PL intensity of the CsPbBr3:Sn@SiO2 retained 46.7% and the Cs4PbBr6:Sn@SiO2 was 59.6% even after 24 h of reaction compared with the initial intensities. These quantum dots with good stability and luminescent property developed in this work are expected to be widely used in light-emitting diodes.
What ideal w-LED phosphors always aim to do is to achieve a single phase near-sunlight emission phosphor simultaneously with both high luminescence efficiency and high thermal stability at operation temperature. And It is well known that apatite compound phosphors are one of the most promising optical materials to realize those above because of their unique structure enhanced luminescence properties and thermal stability. Here, we synthesized a co-doped single phase apatite phosphors Ca 2 La 8 (SiO 4 ) 6 O 2 :Dy 3+ /Sm 3+ (CLSO:Dy 3+ /Sm 3+ ) for white light emission, which was provided with excellent thermal stability and of which luminescence intensity at 150 °C still was 92 percentage of that at room temperature. Moreover, X-ray diffraction technique, Fourier transform infrared spectroscopy, scanning electron microscope were employed to characterization of phase structure and morphology, and consequently pure apatite structure and gravel-like morphology of phosphors were proved. Analysis of photoluminescence spectra indicated that concentration quenching effect exist in single-doped CLSO:Dy 3+ phosphors owing to dipole-dipole interaction between Dy 3+ ions. It is revealed that maybe exist Dy 3+ ↔ Sm 3+ bilateral non-radiative energy transfer processes in Dy 3+ /Sm 3+ co-doped CLSO system by PL spectra and decay curves. And variation of Sm 3+ ion concentration can control color emission, namely CIE chromaticity coordinates and correlated color temperature, finally to achieve white light emission (0.309,0.309) with CCT 6848 K, able to be a potential candidate for commercial lighting applications.
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