The Study On Synthesis And Electro-optical Properties Of Green Quantum Dots With Non-hole-localization Core-shell Structure

As a kind of luminescent materials,the most prominent feature of quantum dots(QDs)is"one kind of material,multicolor luminescence".Because of its excellent monochromatic property and flexible luminescence tunability,quantum dots have broad prospects in display and lighting.How to prepare high-quality QDs is a key factor that restricts the research and application of quantum dot light emitting diodes(QD-LEDs).At present,in the study of CdSe system quantum dots,the CdSe/CdS system is the most studied,and for another material ZnSe,although its lattice matching with CdSe is equivalent to CdS,it can be a good epitaxy for CdSe.However,because researchers often think that ZnSe and CdSe valence band positions are similar,the non-hole-localization will cause the CdSe/ZnSe quantum dots to produce fluorescence blinking,so that there is less research on the CdSe/ZnSe system.In this paper,considering the imbalance of carrier injection caused by the excess of electron injection in the current QD-LEDs structure,the use of ZnSe as a shell helps to reduce the potential barrier of hole injection,thus improving the efficiency of hole injection and achieving high efficiency of QD-LEDs luminescence.We have successfully synthesized the non-blinking CdSe/ZnSe core-shell structure quantum dots by the precise regulation of the shell thickness and the alloying control of the shell interface,and then constructed the efficient QD-LEDs based on the CdSe/ZnSe quantum dot system.The main research contents,results and conclusions are as follows:(1)Preparation of high quality and non-blinking CdSe/ZnSe quantum dots.By exploring the conditions of reaction temperature,solvent ratio and heating rate,a green CdSe/ZnSe quantum dots with quantum yield more than 90%have been synthesized.In particular,the CdSe/ZnSe quantum dots we produced are non-blinking when the ZnSe shell is more than 6 layers.Our work may help the further understanding of the blinking mechanism of CdSe quantum dots since this phenomenon has not been reported before.(2)Prepare high quality CdSe/ZnSe/ZnS and CdSe/ZnSe/ZnSeS/ZnS green quantum dots and build high efficiency QD-LEDs.The fluorescence quantum yields of the two quantum dots are more than 90%,the peak value of the fluorescence is about 530 nm,and the transient fluorescence of the two quantum dots is all single exponential decay.The maximum brightness of QD-LEDs based on CdSe/ZnSe/ZnS quantum dots is as high as 425000 cd/m~2,and the highest EQE reaches 15.8%.In particular,the QD-LEDs based on CdSe/ZnSe/ZnSeS/ZnS quantum dots,the highest EQE is up to 20.06%,and the brightness of more than50000 cd/m~2 can be maintained under the condition of maintaining a EQE exceeding 20%,which is sufficient to meet the requirements of display and lighting.