Synthesis Of Efficient Quantum Dot Hybrid Materials And Its Fluorescent Application Research

QLED device has been widely used in lighting and display mainly owing to its many advantages such as high photoelectric conversion efficiency,high reliability,long service life and so on.Up to now,the green QLED device is still unsuitable for the needs of displayer Market probably owing to its poor light-emitting reliability,brightness,colour performance and so on.As for all kinds of quantum dots for QLED application,semiconductor quantum dots are characterized by the special electrical and optical properties possibly because of their quantum size effect,surface effect,quantum tunneling effect,the quantum confined effect and a series of other unique quantum properties.To enhance the electrical and optical properties of quantum dots,people have been exploring the quantum dots with all kinds of structures.However,there are many inevitable problems for all those quantum dot with different structures,mainly including susceptibility to oxidation(for mononuclear quantum dots),serious lattice mismatch(for shell-core quantum dots),complex fabrication processes(for quantum dots with chemical composition gradients).In order to solve the problems of the quantum dots mentioned above,manganese doped quantum dots with chemical gradient composition have been synthesized by simple single-step liquid reaction route.The highest quantum yield is about 86%,and this quantum dots are further applied to fabricate green QLED device.And the highest brightness can reach 5382 Cd/m2.The specific content has been summarized as follows:(1)Single-core CdSe quantum dots have been synthesized by the oil-phase reaction route,where 1-Octadecene was used as solvent and Oleic acid and Trioctylphosphine as modification agent.Here,single-core CdSe quantum dots have been designed and synthesized under different experimental conditions,and the optimized synthesis process parameters for those single-core CdSe quantum dots with highest quantum yield have been obtained.The highest quantum yield is 46%while the full width at half maximum photoluminescence peaks is 26nm and the stoke displacement is 11nm.The closer the ratio of cadmium and selenium sources is to 4:1,the smaller the photoluminescence peak is,which indicates that when Cd:Se is equal to 4:1,the minimum size of CdSe quantum dots is obtained.At the liquid phase reaction time of 10 min,the sample with highest quantum yield has been acquired,which suggests that in a certain period of time,the longer the reaction time is,the less surface defects are there,the larger PL peak is obtained and the larger size the quantum dots is characteristic of.The synthesis process parameters obtained from this kind of quantum dot will be used as the foundation and reference for other kind of quantum dots in our work;(2)On the basis of the preparation and analysis for the single-core CdSe quantum dots,CdSe/ZnS quantum dots and CdSe/Cd1-xZnxSe1-ySy/ZnS quantum dots have been synthesized,respectively.The performance of CdSe/ZnS quantum dots,especially the quantum yield,has been greatly enhanced mainly owing to the ZnS shell.The highest quantum yield is 81.6%while the full width at half maximum photoluminescence peaks is 34nm and the stoke displacement is 11nm.The closer the ratio of precursors is to Cd:Se=4:1,Zn:S=1:1,the smaller the photoluminescence peak is,the minimum size of CdSe/Cd1-xZnxSe1-ySy/ZnS quantum dots is obtained.With the increase of reaction time,their PL peak gradually become stable and the size of quantum dots gradually become stable.At the liquid phase reaction time of 10 min,the sample with highest quantum yield has been acquired,which suggests that in a certain period of time,the longer the reaction time is,the less surface defects are there,the larger PL peak is obtained and higher quantum yield is acquired.In addition,the composite structure of transition layer between ZnS shell layer and CdSe core layer have been investigated by TEM?PL characterization methods.(3)On the basis of the preparation and analysis for the CdSe/Cd1-xZnxSe1-ySy/ZnS quantum dots,CdSe/Mn:Cd1-xZnxSe1-ySy/ZnS quantum dots have been synthesized by one-step liquid phase reaction route.According the TEM results and PL results,the Manganese is mainly doped and distributed in the Cd1-xZnxSe1-ySy layer of CdSe/Cd1-xZnxSe1-ySy/ZnS quantum dot,and simutaneously larger stoke displacement and higher quantum yield of quantum dots have been observed.The highest quantum yield is 86%while the full width at half maximum photoluminescence peaks is 32nm and the stoke displacement is 16nm.With the increase of reaction time,their PL peak gradually become stable and the size of quantum dots gradually become stable.At the liquid phase reaction time of 5 min,the sample with highest quantum yield has been acquired,which suggests that Manganese element doping can effectively modify the luminescence mechanism of quantum dot.(4)On the basis of the modified fabrication processes for the traditional QLED device,CdSe/Cd1-xZnxSe1-ySy/ZnS quantum dots and CdSe/Mn:Cd1-xZnxSe1-ySy/ZnS quantum dots have been used for fabricate the QLED devices,respectively.After a series of analyses mainly including PL and EL,the QLED device on basis of CdSe/Mn:Cd1-xZnxSe1-ySy/ZnS have delivered the better PL and EL performance than other green QLED device reported in articles.The highest brightness is up to 5382 cd/m.