Synthesis Of High-Quality Orange-Yellow CdZnSe-Based Core-Shell Quantum Dots And Their Study On Luminescent Device

Yellow light-emitting diodes（LEDs）have attracted widespread attention in various opto-electronicfields such as high-quality lighting,displays,photolithography,and signal indication.Currently,the common yellow LEDs in the market are mainly based on Ga In N materials prepared under harsh conditions such as high temperatures and high vacuum,and their expensive manufacturing costs seriously limit their process of scalability and flexibility.Therefore,developing low-cost,solution-processable yellow LED luminescent materials is urgently needed.In recent years,quantum dots（QDs）have developed rapidly due to their advantages such as solution-processability,size-tunable fluorescence emission,excellent color purity,and high quantum yields（QYs）.Since the discovery of the first quantum dot light-emitting diodes（QLEDs）,the performance of QLEDs has been rapidly improved through the development of QDs synthesis,surface chemistry,and device structure.Currently,the external quantum efficiency（EQE）of red,green,and blue QLEDs has all surpassed 20%.However,the insufficient development of QDs in the 560-600 nm range for the emission peak has severely hindered the development and application of orange-yellow QLEDs in high-quality RGBY display panels and white light LEDs.Based on this,this article adopts a strategy of QDs core component regulation and core-shellinterface optimization,designing and synthesizing high-quality orange-yellow Cd Zn Se-based core-shell QDs,the constructed devices with high performance providing a new approach for the development of orange-yellow QLEDs.The specific content is as follows:（1）Using a stepwise temperature increase shell growth strategy to passivate hole defects in QDs,regulate the shell material composition and thickness to reduce hole injection barriers,and synthesize orange-yellow Cd Zn Se/Zn Se/Zn S core-shell QDs with adjustable fluorescence peaks in the range of 575-605 nm,size larger than 11 nm,and QY greater than 95%.Since Cd Se-based QDs and Cd Zn Se-based QDs are both excellent QLED materials,they have potential application prospects in display lighting and outdoor indication.For comparison,this article synthesized Cd Se-based core-shell QDs with the same shell thickness and fluorescence peak.Compared to Cd Se-based QDs,Cd Zn Se-based QDs have higher photochemical stability,single-exponential PL decay and non-blinking characteristics.The devices constructed by Cd Zn Se-based QDs have higher device brightness and EQE,with a maximum EQE of 23.7%,and achieved full orange-yellow emission,with EQE above 20%.（2）Compared with green and red QLEDs,it is urgent to further improve the device brightness oforange-yellow QLEDs.This article further optimize the core-shell interface by coating a thick enough Cd_0.13Zn_0.87Se alloy shell on the Cd Zn Se core,and synthesize orange-yellow Cd Zn Se/6 ML Cd_0.13Zn_0.87Se/5ML Zn S quantum dots with a fluorescence peak at 581 nm,particle size larger than 14 nm,and QY greater than 95%.Due to the further optimization of the core-shell interface,carrier injection is more balanced,resulting in the maximum current efficiency,maximum EQE,and brightness of the device constructed by the quantum dots are 121.8 cd/A,23.4%,and 93.9 w cd/m²,respectively,compared to Cd Zn Se/Zn Se/Zn S quantum dots,the luminance is increased by 40%,and its ultra-high device brightness and excellent stability can make it have broad application prospects in the lighting field.