| Quantum dot-white light-emitting diodes(QD-WLED)have become a promising candidate for “next generation light source for lighting and display”.Normally,red lightemitting QD and yellow light-emiting phosphor are directely mixed with polymer for packaging.However,this traditional packaging method ignores the effect of heat and mass transfer,including the “electric-opto-thermal” convertion inside device,the sedimentation of fluorescent particle,and the moisture permeation,on the performance and reliability of QD-WLED.In order to further improve the overall performance of QD-WLED,it’s need to study the mechanism exploration on the heat and mass transfer during packaging,and propose new encapsulation method for high performance and high reliability packaging.The heat and mass transfer process in QD-WLED packaging has been theoretically modeled and analyzed.First,the “electric-opto-thermal” convertion process and heat transfer channels in QD-WLED was analyzed,and the corresponding one-dimensional thermal resistance network was built to discover the cooling requirment of high-temperature luminescent polymer.Besides,the deposition model of fluorescent particle in polymer was established.Combined with the experimental observation,it is proved that there is a difference in distribution caused by phosphor deposition in QD-WLED.Finally,the mechanism of water vapor dissolution and diffusion in fluorescent polymer was theoretically analyzed,and the optimization direction of silica shell protection was given.In order to solve the overheat problem of fluorescent polymer,the vertically oriented arrangement of flake h BN in fluorescent polymer has been realized by using ice template method,and it was applied to the in-package oriented thermal management of QD-W LED.The experimental results show that h BN filled silicone possesses high transparence and thermal conductivity,and the scattering effect of h BN enhances the light emission intensity of QD.When the mass fraction of h BN is 2 wt%,the thermal conductivity of the h BN/SCMC composite silicone increases by 25%,and the thermal conductivity of the h BN/SCMC layered template reaches 2.2 W/(m·K).The maximum operating temperature of QD-WLED based on h BN/SCMC composite polymer is 15% lower than that of traditional WLED,demonstrating the effectiveness of in-package directional thermal management.The effect mechanism of the differential distribution of fluorescence particle on optical properties has been investigated and an optical consistency packaging technology based on the synchronous deposition of QD and phosphor has been proposed.The sediment-optical coupling simulation was carried out and verified that the synchronous step concentration distribution has more significant optical consistency than the single step concentration distribution.Furthermore,the QD-phosphor composite particle was developed by electrostatic adsorption and the synchronous deposition packaging scheme was verified.The test results showed that the QD-WLED prepared by QD-phosphor composite has better optical stability,and its chrominance coordinate movement is reduced by 62.7% compared with the traditional one.In order to improve the water vapor barrier ability of QD,the moisture-resistant QD with double osmotic hysteresis structure has been proposed.The main preparation technology includes the surface ligand replacement,the silica shell mononuclear coating,and the surface methylation modification.The maded QD nanocomposite has a hydrophobic angle up to 159.6°.After soaking in water for 15 days,the luminescence intensity of superhydrophobic QD nanocomposite maded fluorescent polymer basicly remained stable.However,the luminescence intensity of QD and silica shell-coated QD maded ones decreased by 41% and 24%,respectively.It is proved that superhydrophobic QD possesses excellent water vapor barrier performance. |
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