Synthesis Of CsPbBr₃ Nanocrystals And ZnSeTe Alloy Quantum Dots And Research On Their Luminescence

Quantum dots（QDs）are nanocrystals less than 10 nm in size,and the band gap exhibits quantum mechanical behavior due to their small size.Because of this property,quantum dots can achieve tunable band gap by changing the size and composition.Quantum dot materials have excellent optoelectronic properties and are used in a variety of electronic devices such as solar cells,LEDs,lasers,detectors and optical communications.Although researchers have developed diverse methods for quantum dot synthesis,there are still many problems with quantum dot synthesis,such as the luminescence efficiency,photothermal stability and lead-cadmium toxicity of quantum dots,so in this paper,we will focus on exploring synthetic methods to improve the performance of quantum dots and their applications.The specific research includes the following sections.（1）Semiconductor nanocrystals are inorganic fluorophores with unique optical and spectroscopic properties that can be used as an analytical tool for energy transfer due to their broad spectrum and tunable light emission.The energy transfer process between the materials was explored by synthesized Cs Pb Br₃ quantum dots and nanoplates,and multiple spectral characterizations indicated that energy transfer occurred.A maximum rate of energy transfer of 0.169 ns^-1 and a maximum efficiency of 52%were calculated,and the analysis revealed that the transfer efficiency was related to the acceptor dimension,which explained that the experimental energy transfer efficiency was lower than the transfer efficiency between two-dimensional nanoplates.（2）The halide ion is an unstable factor in cesium-lead halide chalcogenide,and four sets of uniform Cs Pb Br₃ quantum dots of different sizes were synthesized by controlling the imbalance of the halide ion while controlling the temperature.The uniform quantum dots exhibit sharp exciton peaks,so that their Stokes shifts can be clearly observed.It is found that the Stokes shift decreases with increasing size,which is caused by the size-dependent confined hole state above the valence band.Uniform quantum dots also exhibit potential applications as optical gain media and electric absorption modulators.（3）The cooling process of quantum dots is a method to end the reaction,and it was found that slow cooling can enhance the luminescence efficiency and stability of environmentally friendly Zn Se Te alloy quantum dots by modulating the cooling strategy.The best luminescence efficiency of Zn Se Te quantum dots was obtained at a cooling rate of 3 K/min,and its luminescence yield was increased by a factor of 4compared to ice water cooling,while its fluorescence lifetime was increased by a factor of more than 3.Transmission electron microscopy morphology characterization demonstrates that slow cooling improves crystal crystallinity and shell layer thickness,while XRD structural characterization demonstrates that atoms diffuse to form a gradient structure,and transient spectroscopy directly observes that cooling reduces non-radiative composite defects in the material,all of which are beneficial to enhance the luminescence efficiency of quantum dots.The cadmium-free Zn Se Te quantum dot materials also exhibit potential as white light-emitting diodes and visible light optical communication.