Study Of Optical Properties Of Quantum Dots@Silica Core-Shell Nanoparticles

Colloidal semiconductor quantum dots,abbreviated as QDs,are widely used as light conversion materials in display backlighting and solid-state lighting due to their unique optical properties.QDs are generally used to prepare fluorescence-converting light-emitting diodes（QCLEDs）by mixing with silicone gel,but the performance of the devices were limited by the poor stability and dispersion of QDs in silicone matrices.Encapsulating QDs with SiO₂ shell through microemulsion method is an effective measure to improve their stability and miscibility in silicone to prepare the structure of QDs@SiO₂.However,there is lack of sufficient research on the impact of catalyst species on the morphology and optical properties of core-shell QDs@SiO₂,as well as the influence of SiO₂ shell thickness on the luminescence properties of QDs are lacking systematic research.This thesis focuses on studying the influence of different catalysts on the morphology and efficiency of QDs@SiO₂ in the preparation process.At the same time,the impact of the SiO₂ shell thickness on the optical and thermal properties of QDs@SiO₂ in QCLEDs is studied in depth.The detailed research contents include:（1）Controlled synthesis of QDs@SiO₂ core-shell structures.Spherical Cd Se/Zn S QDs@SiO₂ and rod-like Cd Se/Cd S QDs@SiO₂ were prepared based on microemulsion method.QDs@SiO₂ were prepared by various catalysts and catalysts with different concentrations.By comparing the morphology and optical properties of the core-shell QDs@SiO₂,it is concluded that the morphology of the QDs@SiO₂ mainly depends on the morphology of the QDs.Both ammonia and methylamine solution can successfully catalyze the microemulsion reaction,but the different basicities of the two catalysts lead to differences in reaction rates and optical properties of the products.The QDs@SiO₂ nanoparticles and QCLEDs show optimal optical properties when the methylamine concentration is about 10 wt%.However,butylamine has weak catalytic ability and hence it is difficult to effectively control the growth of SiO₂ and encapsulation of QDs.（2）Research on the optical properties of QDs@SiO₂ nanoparticles.Based on the above preparation method,spherical Cd Se/Zn S QDs@SiO₂ with a SiO₂ shell thickness ranging from 10to 60 nm were prepared.The combined effects of light scattering,thermal accumulation,and concentration quenching of different nanoparticles on the optical properties of QCLEDs were investigated by optical and thermal simulations combined with experimental tests.The results show that the optimal optical performance of QDs@SiO₂ nanoparticles is achieved with SiO₂ shell layer thicknesses in the range of 20-30 nm,which effectively suppresses the self-absorption quenching and enhances light scattering of the QDs@SiO₂ at low power density environments.At a high power density,thermal accumulation occurs within the QDs@SiO₂ nanoparticles,and a thinner SiO₂ shell layer,ranging between 10-15 nm,is more conducive to reduce the thermal quenching of QDs in QCLEDs while maintaining their luminous efficiency.This study provides guidance for the development of an appropriate QDs@SiO₂ structure to meet the application requirements of different QCLED devices.