Research On Efficient And Environmental Friendly InP Quantum Dots

Quantum dots(QDS)are widely used in bioluminescence,cell imaging and other fields due to their well-coordinated and excellent photoluminescence properties.In recent years,cadmium-based quantum dots,led by Cd Se,have been widely adopted.However,the biological toxicity of cadmium compound limits the application of cadmium-based quantum dots in immune analysis,biomedicine and other fields,causing great harm to the environment and human body.The research object of this project is cadmium-free quantum dot indium phosphor(InP),and the luminescence principle,synthesis method and device application are also explored.However,at present,the quantum yield of InP QD is still relatively low,and large-scale production cannot be achieved,which seriously restricts the application of InP QDs.In this paper,the study of core-shell structure is conducted to solve the problem of low quantum yield of InP quantum dots.The InP core is coated with different shells and different shell thickness :InP/ZnSe,InP/ZnSe/ZnS,InP/ZnS,InP/ZnS/ZnS four shell structured quantum dots,by contrasting,analysis and find that zinc selenide(ZnSe)to some extent can solve the problem of band gap and the lattice constant(5.66 A),but because ZnSe potential barrier is small,the electrons and holes within the core is not easy to be restricted,and is very easy to jump into the shell,causing spectrum redshift.In order to get the green light,the shell thickness of ZnSe needs to be increased to limit the transition of holes and electrons,which can make colour more pure.The smaller the volume gets,the larger the specific surface area is.As a result,the surface defects increases,the quantum yield reduces,also its chemical stability limits the application of ZnSe.Whereafter,we explored the InP/ZnSe/ZnS,InP/ZnS/ZnS double shell structure,find that DDT ligand is replaced by the TOP when covering the second ZnS layer,causing the formation of defect mode.Therefore,the QY decreases.By exploring the optimal reaction temperature,time and materials ratio,we finally find that zinc sulfide(ZnS)is the optimal cladding layer,which better limits the transition of electrons and holes,and the obtained InP quantum dots have better stability and higher quantum yield.The maximum quantum yield and external quantum efficiency obtained was 75.1% and2.7% respectively.We also explore the InP/ZnSe/ZnS,InP/ZnS/ZnS double shell structures,the stability of the quantum dots can be increased by increasing the thickness of the shell.