Research On Synthesis And Optical Properties Of CsPbX₃(X=Cl?Br?I)Perovskite Quantum Dots

The all-inorganic perovskite quantum dots for CsPbX₃(X=Cl,Br,I)have excellent optical properties,such as adjustable band gap,high luminous efficiency and single-color luminescence.Therefore,they have good application prospects in laser,display and photoelectric detection.However,the structure of CsPbX₃ quantum dots is easily damaged by O₂ and H₂O in humid air,which cause the instability and quenching of luminescence,limiting their wide applications in the field of optics.Therefore,it is extremely urgent to optimize optical properties and enhance luminescence stability for CsPbX₃ quantum dots.The research mainly focuses on the structure,morphology,optical properties and light stability of CsPbX₃ quantum dots and their composite nanomaterials.On the basis of CsPbBr₃ quantum dots,Cs Pb Cl₃ and Cs Pb I₃ quantum dots are obtained by the anion substitution method,which can achieve wide-band luminescence in the full visible spectrum.In addition,the hydrophobic polymers for PMMA and paraffin are used to coat the CsPbX₃ quantum dots.It is found that the PMMA and paraffin wax all can effectively improve the optical stability of CsPbX₃ quantum dots.The main research contents of the paper are as follows:(1)To realize the wide-band luminescence for CsPbBr₃ quantum dots,Cs Pb Cl₃ and Cs Pb I₃ quantum dots are obtained based on CsPbBr₃ quantum dots with great luminescence properties by the anion substitution method,such as Cl^-replace Br^-and I^-replace Br^-.By adjusting the molar ratio of Cl^-to Br^-or I^-to Br^-,the wide-band luminescence for CsPbBr₃quantum dots are realized in the full visible spectrum from 424 nm to 664 nm.Due to the crystal structure and the size effects of quantum dots,with the increase of Cl^-,the sizes are gradually decreasing,and the fluorescence emission peaks are gradually blue-shifting for CsPbBr₃ quantum dots.After complete anion replacement from Br^-to^-Cl^-,the Cs Pb Cl₃quantum dots are obtained.Under ultraviolet light irradiation,Cs Pb Cl₃ quantum dots emit bright blue-violet fluorescence with an emission peak at 424 nm.With the increase of I^-,the sizes of CsPbBr₃ quantum dots gradually increase,and the fluorescence emission peak is gradually red-shifted.After complete anion replacement from Br^-to^-Cl^-,the Cs Pb I₃quantum dots are obtained.Under ultraviolet light irradiation,Cs Pb I₃ quantum dots emit the bright red fluorescence with an emission peak at 664 nm.At room temperature,compared to luminescence stability,it was found that the fluorescence quenching of Cs Pb Cl₃ and Cs Pb I₃ quantum dots occurred only more than ten days in the air,but the fluorescence quenching of CsPbBr₃ occurred completely for 21 days.It shows that the luminescence stability of CsPbBr₃ quantum dots are stronger than Cs Pb Cl₃ and Cs Pb I₃quantum dots in the air.When the three were added to water,the fluorescence quenched completely after only 2 to 3 minutes.(2)To enhance the luminescence stability of CsPbX₃ quantum dots,the hydrophobic polymers for PMMA and paraffin are used to coat the CsPbX₃ quantum dots.Compared the optical properties and luminescence stability before and after coating,the results show the peak position,peak shape and peak intensity of CsPbX₃ quantum dots have not been effected by the PMMA or the paraffin,but the complete fluorescence quenching of CsPbX₃quantum dots are caused in about 20 days in the air,while the CsPbBr₃/PMMA composite nanomaterials are placed in air and water for 90 days,maintaining 69%and 41%of their initial luminous intensity.In addition,the three representative CsPbX₃/paraffin composite nanomaterials are placed in air and water for 63 days,maintaining 56%and 58%,73%and 66%,57%and 55%of their initial luminous intensity.The above research shows that the introduction of PMMA or paraffin effectively enhanced the luminescence stability of CsPbX₃ quantum dots.The research provides the important experimental support and theoretical basis for the application of CsPbX₃ quantum dots in light-emitting devices.