Preparation And Application Of Halide Perovskite And Metal-organic Framework Composites

Perovskite materials have many advantages such as high carrier mobility,high fluorescence quantum yield,and easy synthesis due to their diverse types and flexible and adjustable crystal structures.They have great potential for applications in fields such as light-emitting diodes（LEDs）,spectral analysis,biological imaging,and optical communication.However,the stability problem of lead halide perovskites,the problem of lead biotoxicity,the problem of large-scale synthesis,and the problem of application limitations after combination with other materials restrict their practical application.In view of these shortcomings,this paper prepares suitable metal-organic framework materials（MOFs）and perovskite quantum dot materials to synthesize stable luminescent composite materials.According to the performance characteristics of the new materials,they are respectively used for heavy metal ion detection in water quality,LED device luminescence and lead-free perovskite fluorescent material white light emission.The specific work is as follows:1.ZIF-7 material was selected and CsPbBr₃@ZIF-7 composite material was prepared using the thermal injection method to investigate its fluorescence characteristics and its application as a mercury ion probe in aqueous solution.The prepared CsPbBr₃@ZIF-7 material stably emits green light with a wavelength of521nm under 365nm UV,and its solid powder did not show obvious fluorescence decay after 90 days in air or after being immersed in water for 2 hours.Based on the stability of CsPbBr₃@ZIF-7 in aqueous solution and its sensitivity to Hg²⁺,CsPbBr₃@ZIF-7 powder was used as a fluorescent probe to detect Hg²⁺pollution in aqueous solution,showing reliable sensitivity.2.A light-emitting diode（LED）with a MAPbBr₃@ZIF-11 crystal thin film as the functional layer was prepared.Based on the small particle size（30-50nm）of ZIF-11 in MOFs materials,a two-step method was used to in-situ grow a luminescent thickness（<300nm）MAPbBr₃@ZIF-11 crystal thin film as the functional layer on a glass/ITO/PEDOT:PSS substrate.TPBi,LiF,and Al were vacuum-deposited as the electron transport layer,buffer layer,and cathode,respectively.The device structure was glass/ITO/PEDOT:PSS/MAPbBr₃@ZIF-11/TPBi/LiF/Al.Benefit of the protection of ZIF-11,the device achieved stable operation for more than 50 hours under continuous UV irradiation,heat and electrical stress.3.High-stability lead-free MASnBr₃@ZIF-11 fluorescent powder is prepared for pure white light emission.Using thermal injection combined with template method to grow MASnBr₃quantum dots in ZIF-11 cages with rigid skeletons.Octadecene and DMF are used to wash away large particle perovskite nanocrystal impurities generated during synthesis to obtain purified MASnBr₃@ZIF-11 material.The extremely small particle size（1.5nm）and uniform size MASnBr₃quantum dots in ZIF-11 cages exhibit obvious quantum confinement effects.Under 365nm UV excitation,MASnBr₃@ZIF-11 emits blue light at 450nm with an emission half-width less than18nm,showing excellent color purity and PLQY reaching 23.5%,exceeding the previous record of tin-based perovskite quantum dots at 17.4%.At the same time,due to ZIF-11’s rigid small pore size（0.30nm）,it effectively prevents water and oxygen（0.34nm）from invading,especially Sn²⁺valence state is well protected.After three months in natural environment,the material maintains more than 95%PL intensity;Iodine ions are doped to prepare MASnBr_XI_3-X@ZIF-11 materials that emit 520nm green light and 620nm red light respectively,both showing equally excellent color purity and stability.The three primary color composite materials are mixed with silicone resin in proportion to make a white light device.This white light device has CIE（Commission Internationale de l’Eclairage）（0.31,0.30）,close to the standard white light emission coordinates（0.33,0.33）.During the operation of the luminescent device,PEQDs can be well protected and will not be affected by oxidation,ion migration or quantum dot aggregation,maintaining stability for more than 500 hours.