Preparation Of Cesium Lead Bromide Nanocrystals In Microchannel-reactor And Application In Light-emitting Diodes

LEDs have been widely used in lighting and backlight fields,instead of incandescent lamp,fluorescent lamp and other traditional light sources.Due to the advantages of low cost,low consumption and high adjustability,the cesium halide nanocrystals are expected to replace the conventional phosphors,improve the optical properties of LED products and promote the development of LED industry.In order to meet the requirements for efficient crystal preparation in LED application,microchannel-reactor has been studied,because of its numerous advantages including high efficiency of heat and mass transfer,high degree of automation,etc.In this paper,the internal structure of microchannel-reactor were designed and optimized by flow simulation,the influence of microchannel process parameters on the optical and phase properties were studied,and the LED devices with high light color quality were manufactured by using the nanocrystals.In theory,the numerical model and grid were established firstly,based on the related theoretical analysis of hydrodynamics.Then the grid parameters for simulation were determined according to the grid quality standard and non-correlation test in ANSYS software.A series of simulation on the fluid in microchannels with different width and depth were carried out.After that,the distribution of fluid was analyzed by volume fraction cloud diagram,velocity vector diagram,streamline diagram and the calculated mixing-strength.Therefore,the optimal shape parameters of microchannels were obtained and the subsequent micro-reactor system was built.In the preparation process of microchannel-reactor,the influence of microchannel-reactor parameters on the crystallization process was studied,based on the serpentine microchannel optimized by flow analysis.The detection methods involved include X-ray diffraction,electron microscopy,X-ray photoelectron spectroscopy,energy dispersive X-ray spectroscopy,etc.By adjusting the microchannel temperature,the flow rate and the ratio of the fluid,the Cs Pb Br₃nanocrystals with adjustable particle size,absorption spectrum,emission spectrum and half peak width were obtained.What's more,the Cs Pb Br₃/Cs₄Pb Br₆ nanocrystals with adjustable phase and morphology were gained at different flow rate.In the application of LED,the nanocrystals collected in microchannel-reactor were introduced,and the parameters of fluorescent conversion layer were studied based on the structural characteristics of top and remote excitation LED devices.For top LED devices,the reflectivity and light intensity were analysed to improve the device contrast and anti-interference ability.In addition,the optical and thermal properties of different device structures were explored by light flux,light efficiency,space color temperature and surface temperature,to obtain remote excitation LED devices with higher conversion efficiency,more uniform light color and stronger heat dissipation.