Controllable Preparation Of Blue ZnTeSe-based Core-Shell Quantum Dots And Their QLED Performance

Semiconductor colloidal quantum dot materials are expected to become the next generation of main display lighting materials due to their excellent characteristics,such as tunable emission peak position,good light stability,wide excitation spectrum and narrow emission spectrum,long fluorescence lifetime,etc.With the development of quantum dot material synthesis process and quantum dot light-emitting diode(QLED)technology based on quantum dot materials for decades,the current QLED based on mainstream red and green quantum dot materials containing heavy metal systems can basically meet the needs of quantum dots in the field of lighting and display.However,the performance of blue QLED needs to be further improved,especially environmentally friendly blue devices,which limits the commercial application of quantum dot materials.Zinc selenide(ZnSe)quantum dots can emit size-dependent fluorescence in the blue and near-ultraviolet regions due to their wide bulk band gap and small Bohr radius.The ZnTeSe-based ternary system quantum dots can be further prepared by Te doping,which can effectively play the advantages of continuously adjustable fluorescence peak position of quantum dots by adjusting the composition of crystal nucleus.Therefore,environmentally friendly blue ZnTeSe-based quantum dot materials are of great research value.However,the surface effect caused by small size will cause many dangling bonds and surface defects on the surface of ZnTeSe quantum dot crystal nucleus,resulting in non-radiative recombination,low photoluminescence quantum yield(PLQY)and poor stability.Moreover,its wide band gap makes it difficult to inject holes when the device is working,resulting in excessive injected electrons accumulating at the interface and causing non-radiative recombination,which is not conducive to the improvement of device performance.Based on this,this paper studies the synthesis process of blue ZnTeSe-based core-shell quantum dots and constructs QLED.The main work is divided into the following two parts :(1)Regulation and optimization of ZnTeSe:ZnSe crystal nucleus.The preparation of high-quality blue ZnTeSe-based quantum dot materials must first prepare high-quality blue ZnTeSe crystal nuclei.The ZnTeSe crystal nucleus is almost non-fluorescent due to the surface effect caused by the small size,which poses a new challenge to the characterization of ZnTeSe crystal nucleus quality.Based on this,this paper studies the structure of ZnTeSe and ZnTeSe:ZnSe nuclei,and proposes a method to study the quality of nuclei according to the optical properties of ZnTeSe:ZnSe nuclei.Firstly,the nucleation temperature and growth time of ZnTeSe:ZnSe crystal nucleus were experimentally explored to explore the best nucleation method at high temperature.Then,the stoichiometric ratio of ligands,precursors and drugs of ZnTeSe:ZnSe crystal nucleus was experimentally regulated to select the best experimental conditions.Subsequently,the optical phenomenon of Te doping in ZnTeSe:ZnSe crystal nucleus was studied,and ZnTeSe-based ternary system quantum dots were prepared.It is expected to alleviate the lattice mismatch between ZnTeSe and ZnS shell,improve the photoluminescence quantum yield PLQY of quantum dots,and adjust the fluorescence peak position of crystal nucleus by Te doping to make it closer to the pure blue fluorescence range.Finally,the further epitaxial growth mode of the crystal nucleus and the precursor design experiment were explored,and the epitaxial growth mode of the rapid injection precursor was explored.The high-quality crystal nucleus was prepared by a simple method,which laid the foundation for further shell passivation and preparation of QLED.(2)Synthesis of ZnTeSe:ZnSe/ZnS core-shell quantum dots and their application in QLED.The ZnTeSe:ZnSe crystal nucleus is further passivated by coating the shell layer,which can increase the size of the quantum dots while protecting the ZnTeSe:ZnSe crystal nucleus,effectively alleviate the surface effect,and inhibit the F(?)rster resonance energy transfer phenomenon of the quantum dot luminescent layer film.Therefore,it is necessary to study the design and thickness control of ZnTeSe-based quantum dot shell.Firstly,the effect of crystal nucleus purification on the subsequent shell coating was studied,and a more suitable purification method for the synthesis of quantum dots in this system was explored,which laid a foundation for the subsequent effective shell coating.Then,the optical properties and device performance of ZnSe Te:ZnSe/ZnSe S/ZnS core-shell quantum dots and ZnTeSe:ZnSe/ZnS core-shell quantum dots were compared,and the ZnTeSe:ZnSe/ZnS core-shell quantum dots with better performance were selected for subsequent shell thickness control.Subsequently,ZnTeSe:ZnSe/ZnS core-shell quantum dots with a thickness of about 10 nm were prepared by continuously injecting precursors.Finally,in order to further improve the quality of quantum dots and the performance of QLED,this paper focuses on the role of hydrofluoric acid etching in the process of synthesizing quantum dots,and then prepares near-single-channel radiation composite ZnTeSe:ZnSe/ZnS core-shell quantum dots,and the external quantum efficiency of the QLED constructed is up to 15 %.In this paper,the synthesis process of blue ZnSe-based quantum dot materials is studied and improved,and high-quality blue ZnTeSe:ZnSe/ZnS core-shell quantum materials are prepared,which promotes the development of environmentally friendly blue quantum dot synthesis process and promotes the preparation technology upgrade of environmentally friendly blue quantum dots.