Aixiang Wei

High-Power Light-Emitting Diodes Package With Phase Change Material

We report the fabrication and charaterization of high-power light-emitting diodes (LEDs) package with phase change material. Paraffin wax with melting point of 49.6 °C was inserted between the LED die and silicone encapsulant. The phase changing of embedded wax in a working LED is observed by studying its output flux and junction temperature. With a driving current density of 443 mA/mm

Influence of Deposition Parameters on the Morphology, Structural, and Optical Properties of ZnSe Nanocrystalline Thin Films

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Synthesis and characterization of CdSe nanocrystalline thin films deposited by chemical bath deposition

, LED sample demonstrates a decreasing of junction temperature by 19 °C and an increasing of light flux by 25% with the insertion of 6-mg paraffin wax. Optical and thermal simulations are employed to analyze the improved performance of LED package. Higher thermal conductivity of paraffin wax compared with silicone resin is considered to be reason for LEDs reduced junction temperature. The high refractive index of paraffin wax is considered to be the dominant mechanism of LEDs enhanced emission.

Preparation and characterization of ZnS thin films prepared by chemical bath deposition

Zinc selenide (ZnSe) nanocrystalline thin films were prepared by using chemical bath deposition at different ammonia concentrations and different deposition temperatures. The structural and optical properties of ZnSe nanocrystalline thin films were investigated as a function of the ammonia concentration in precursors or the deposition temperature using scanning electron microscopy, energy-dispersive spectrometry, x-ray diffraction measurements, and ultraviolet (UV)–visible spectrophotometry measurements. The results reveal that the ZnSe thin films are composed of a large number of uniform spherical particles. Each spherical particle contains several nanocrystals 5xa0nm to 7xa0nm in crystallite size. An increase in both the average diameter of the spherical particles and the crystallite size of the nanocrystals occurs with an increase in ammonia concentration and/or deposition temperature. The Se/Zn atom ratios in the ZnSe thin films increase and the optical band gaps, Eg, of the ZnSe thin films decrease with an increase in ammonia concentration or deposition temperature. The kinetics and reaction mechanism of the ZnSe nanocrystalline thin films during deposition are discussed.