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Major Steps made in HFUT Studies on LED Fluorescent Materials
time: Jan 23, 2016

The research group formed by Associate Professor Chen Lei and Professor Jiang Yang yielded major progress in Yttrium aluminum garnet (YAG) structures and quantum dot composite LED fluorescent materials. The results were published on Scientific Reports, one of Nature’s open-access journals, and Green Chemistry published by the Royal Society of Chemistry.

The title of one study is “Charge deformation and orbital hybridization: intrinsic mechanisms on tunable chromaticity of Y3Al5O12:Ce3+ luminescence by doping Gd3+ for warm white LEDs”.

YAG is an important crystal which can be applied in solid laser host and scintillation detectors. Y3Al5O12 (YAG:Ce) is an important yellow phosphor for LED. The substitution of Y3+ by Gd3+ would shift the chromaticity of LEDs from white to warm white, but with low luminescence efficiency and thermal stability. The phenomenon cannot be explained with the traditional configuration coordinate diagram.

Professor Chen applied modern laboratory techniques such as X-ray absorption fine structure (EXAFS) and ultraviolet photoelectron spectra (UPS), and electronic band structure theory to prove that when Y3+  is substituted by Gd3+,  the YAG structure should become more rigid because Gd3+ has a larger radius  in comparison with Y3+ and thus it will suffer intensive compression from other neighboring atoms in the rigid structure.

In summary, a new interpretation from the viewpoint of compression deformation of the electron cloud in a rigid structure by combining hybrid orbital theory with solid-state energy band theory together has been put forward in this work to illustrate the intrinsic mechanisms that cause the emission spectral shift, thermal quenching, and decrease in intensity of YAG.

In terms of quantum dot composite LED fluorescent materials, Chang Yajing, a PhD student in the group, developed a new green chemistry approach to synthesize high quality quantum dot-inorganic salt composites. The approach is green, simple, environmentally-friendly, low-cost and available for large-scale industrial application. The study was published on Green Chemistry as an Advanced Article.

HFUT studies on LED Fluorescent Materials were jointly funded by 863 Program (State High-Tech Development Plan), National Natural Science Foundation of China, Research Fund for the Doctoral Program of Ministry of Education and Anhui Key Technologies Program.

Writer: Zhong Min

Editor: Guan Qian