Synthesis And Properties Of Doped APbBr₃?A=MA,Cs? Perovskite Luminescent Materials At Room Temperature

Lead based halide perovskite luminescent materials have attracted much attention because of their wide application prospects in lighting,display,sensing,biological imaging and other fields due to their advantages of narrow emission peak,high color purity and adjustable emitting wavelength.Among lead halide perovskites,APbBr3?A=MA,Cs?perovskite quantum dots are the research hotspot due to the simple structure and high fluorescence quantum yield?PLQY?.However,the instabilities of the structure and spectrum seriously hinder their further development and application.In addition,these materials are usually prepared by the hot injection method,and the experimental conditions are very harsh,such as requiring synthesis under high temperature,vacuum environment or inert gas protection,which is a challenge for large-scale industrial production.Therefore,based on the electronic regulation strategy,we have successfully prepared NH₄⁺doped MAPbBr₃ quantum dots?QDs?,Sn²⁺doped CsPbBr₃ quantum dots and Cl^-/I^-doped CsPbBr₃ QDs at room temperature?RT?by improving the ligand-assisted re-precipitation?LARP?,and systematically studied their properties.The introduction of doping ions changes the electronic structure of the original perovskite materials,which improves the instabilities of the structure and spectrum,and also greatly boosts their PLQY.This work includes the following three aspects:1.The structural and spectral instability of MAPbBr3 QDs is a great challenge for researchers.Herein,we introduce NH₄⁺ions into MAPbBr₃ QDs at room temperature to partially replace the A-site MA⁺ions,and successfully prepare super stable blue light MA_0.5?NH₄?_0.5PbBr₃ QDs.Experimental characterization and theoretical calculation show that NH₄⁺with large lattice formation energy partially replaces MA⁺to form a stronger ion bond with Br^-ions,which not only leads to larger binding energy and improves the structure stability,but also increases the crystallinity and thus reduces the defects located at the crystal surface and inside,finally decreases the non-radiative transition of excitons?The PLQY is up to 99.79%,which represents the highest value in blue lead halide perovskites to date?.2.Sn²⁺is often used to partially replace Pb²⁺at B position of lead-based perovskite,which not only reduces the toxicity,but also improves the stability.However,CsPb_1-xSn_x Br₃?x=0.0-0.9?QDs reported so far have been synthesized by traditional hot injection?HI?method.Moreover,the stability and PLQY of these QDs are not high.Thus,we successfully prepared CsPb1-xSnxBr3?x=0.0-0.9?QDs at room temperature for the first time.The results show that the QDs obtained by the RT method is more stable,the PLQY is higher?the optimal PLQY is 91%?than that obtained by the HI approach,and it still maintains more than 80%of its original fluorescence strength after 120 days in air environment.Because of the superior PLQY,light-emitting diodes?LEDs?based on the RT-QDs is constructed,and it exhibits an external quantum efficiency?EQE?of 1.8%,a luminance of 1600 cdm^-2,a current efficiency of 4.89 cdA^-1,showing a good application prospect.3.Herein,RT-CsPbBr₃ QDs were obtained based on the second work,and then CsPb?X/Br?₃?X=Cl^-,I^-?perovskite QDs were successfully prepared by introducing Cl^-and I^-ions into the crystal to replace the X-position Br^-ones by ion exchange method.Due to the different radii of the three anions,their different proportions in the crystal lead to the formation of nanocrystals with different particle sizes,thus realizing the adjustment of the luminescence of CsPbBr3 QDs in the whole visible light range?419-670 nm?.In addition,we used KCl and KI as reagents in the QDs preparation,which expands the application of non-toxic and cheap inorganic salts in the synthesis of high-quality perovskite materials.The present work provides an effective method for large-scale synthesis of various halogenated perovskite materials at room temperature.