Study On The Synthesis Of Highly Efficient Zn-Se-Te Alloy Blue Quantum Dots And Their Electroluminescent Devices Performance

Blue light-emitting devices are the key to realize full-color display of quantum dot lightemitting diodes(QLEDs).ZnSeTe alloy blue-light quantum dots have attracted much attention in recent years due to their have not heavy metal and are friendly to the environment.However,ZnSeTe alloy quantum dots have the disadvantages of the rapid oxidation of ZnTe bonds and the wide band gap of ZnSeTe alloy quantum dots makes the charge transport difficult,making the synthesis of high photoluminescence quantum yield(PLQY)ZnSeTe materials and the fabrication of ZnSeTe-based highly efficient QLEDs very difficult.Based on this,this thesis aims at the problems that restrict the external quantum efficiency(EQE)of quantum dot light-emitting diodes,such as poor stability,low photoluminescence quantum yield and wide half-peak width of ZnSeTe alloy quantum dots.High-quality ZnSeTe/ZnSe/ZnS quantum dots were synthesized by coating shells,and halogens were used to passivate the defects on the surface of quantum dots and eliminate the long chain ligand which improving the performance of charge transport and radiative combination rate of quantum dots and constructing high-efficiency ZnSeTe/ZnSe/ZnS QLEDs.The specific experimental results are shown as follows:(1)The optical properties and stability of quantum dots were enhanced by coating the ZnSe/ZnS shell layer and the reactivity of the Se precursor was improved by using DPP-Se instead of TOP-Se which would be beneficial to synthesize high-quality ZnSeTe/ZnSe/ZnS quantum dots.The half-peak width of final synthesized ZnSeTe/ZnSe/ZnS core/shell quantum dot was reduced from nearly 30 nm to 22 nm and the photoluminescence quantum yield of final synthesized ZnSeTe/ZnSe/ZnS core/shell quantum dot was increased from original 1.28%to 44.3%.(2)The charge transport performance of QDs was improved by eliminating the longchain organic ligand trioctylphosphine on the surface of quantum dots through chloroform post-treatment.The average lifetime of quantum dots was increased from 37.1 ns to 65.2 ns and the PLQY of quantum dots was increased from 39.6%to 92.0%due to chloride ion as a byproduct passivated the defects of QDs surface.What’s more,the performance of blue QLEDs was also greatly improved,with a three-fold increase in the external quantum efficiency from 0.62%to 2.25%and a reduction in turn-on voltage from 6.3 V to 5.1V.(3)The bromine ion modification can improve the photovoltaic properties of ZnSeTe/ZnSe/ZnS blue quantum dots,which was further verified theoretically and experimentally.By bromine ion modification,the PLQY of ZnSeTe/ZnSe/ZnS quantum dots was enhanced from 39.7%to 86.2%,the carrier lifetime was extended from 32.03 ns to 50.76 ns,and the non-radiative recombination rate was reduced from 18.83 μs-1 to 2.72 μs-1.At the same time,the device performance has been greatly improved,with a seven-fold increase in external quantum efficiency from 0.74%to 5.46%and a reduction in turn-on voltage from 6.7 V to 5.9 V.