Synthesis And Optical Stability Improvement Of Multicomponent Perovskite Quantum Dots

Perovskite quantum dots(PQD)are one of the most important nano-level light-emitting semiconductor materials.Because of its adjustable band gap,excellent charge transfer,high theoretical photoelectric conversion efficiency and other unique photoelectric characteristics,it has attracted the attention of researchers.Due to its own structural defects,exposure to light,heat and air will cause irreversible degradation,which affects the luminous efficiency.Therefore,the practical application of quantum dots is greatly limited.At the same time,most of the research on perovskite quantum dots contains Pb element.Considering the inherent instability and toxicity of Pb,the study of low toxicity,green and environmentally friendly lead-free perovskite nanomaterials is of great significance.In this paper,CsPbBr₃/n Cd S/Al₂O₃ quantum dots were successfully prepared by thermal injection and homogeneous ligand coating Al layer;bismuth-based lead-free Cs₃Bi₂Br₉ quantum dots were prepared by antisolvent method at room temperature,and surface coated with SiO₂ and surface passivation The multiple protection method combining DDAB and surface-coated SiO₂ modifies the defect state of the quantum dot surface,thereby improving the stability of the quantum dot.Through fluorescence spectroscopy,lifetime and variable temperature PL analysis,the intrinsic luminescence mechanism of quantum dots was analyzed,and their stability was tested accordingly and applied to electroluminescent devices.The details are as follows:CsPbBr₃/nCdS/Al₂O₃ QD was successfully prepared by alternating ion layer adsorption growth method,which improved the fluorescence intensity of quantum dots and effectively improved their light stability.The test results show that the Al doped in the shell can be oxidized to Al₂O₃ and effectively prevent further photodegradation during long-term light irradiation.Using its luminescence stability,flexible electroluminescent device was successfully prepared.The variable temperature PL spectrum of CsPbBr₃/nCdS/Al₂O₃ quantum dots observed that with increasing temperature,the PL intensity of CsPbBr₃/3CdS/Al₂O₃ core/multi-shell quantum dots changed less,and the degree of blue shift weakened.This indicates that the non-radiative recombination in the multi-shell coating is significantly suppressed.Using ligand-assisted precipitation method,ethanol as anti-solvent to prepare lead-free Cs₃Bi₂Br₉quantum dots.At the same time,due to the introduction of water in the antisolvent,the addition of ethyl orthosilicate induced the formation of a SiO₂protective layer on the surface of Cs₃Bi₂Br₉ quantum dots without changing the crystal structure of the quantum dots.The quantum dots coated on the surface of SiO₂ with different shell thicknesses showed high stability under the air exposure for more than60 days and prepared lead-free bismuth-based quantum dot light-emitting devices.Simultaneously,the luminescence intensity,emission peak position and half-height width of Cs₃Bi₂Br₉/SiO₂ quantum dots in the temperature range of 10-300K with temperature are studied.The results show that the emission of quantum dots mainly comes from exciton recombination.The ligand-assisted precipitation method was used to prepare bismuth-based lead-free Cs₃Bi₂Br₉ quantum dots,adding an appropriate amount of DDAB to modify the surface defect state of the quantum dots,and then introducing SiO₂ to coat the surface of the quantum dots to further improve the stability of the quantum dots through multiple protections without affecting the luminescence strength.Stability tests show that the surface passivation and coated quantum dots still maintain good luminescence performance after being placed in an open environment for two months.The temperature-dependent PL spectrum can be used to understand the radiation of quantum dots,the non-radiative relaxation process and the exciton-phonon interaction.