Preparation And Optical Properties Of Inorganic Perovskite-Polymer Composites

All-inorganic perovskite quantum dots have many advantages,such as high fluorescence quantum yield,narrow emission bandwidth,wide absorption cross-section,tunable emission spectrum in the whole visible spectrum,so they have attracted wide attention of researchers in a relatively short period of time and become one of the superstar materials in the field of luminescent materials and photoelectric devices.Although it has good prospects for development in the fields of light emitting diodes,photodetectors,lasers and so on,poor stability is one of the main difficulties hindering its further development and meeting practical application standards.The main reason for the poor stability is that all inorganic perovskite quantum dots are very sensitive to oxygen and water.In addition,light and heat can further lead to serious degradation and agglomeration of nanocrystals,resulting in a sharp reduction in fluorescence quantum yield.In this paper,the strategy of preparing composite materials by combining all-inorganic perovskite quantum dots with polymers is proposed,which can effectively isolate oxygen and water while guaranteeing their excellent luminescent properties,and greatly improve the stability of all-inorganic perovskite quantum dots in air and water.Specific research contents are as follows:Firstly,all-inorganic perovskite quantum dots CsPbX₃?X=Cl,Br,I?with different halogen types and ratios were prepared by thermal injection method.The size of nanocrystal is about 12 nm,the emission wavelength can be adjusted between 420-690 nm,and the fluorescence quantum yield can reach 40-90%.Subsequently,we adopt a convenient and rapid ultraviolet polymerization method to prepare perovskites-polymer composites using inexpensive,environmentally friendly commercial epoxy resin.The photoluminescence?PL?spectrum shows that the composites can well retain the luminescent colors of the original solutions,and the emission peak position is basically unchanged.We monitored its luminescent stability:its emission peak position and luminescent intensity remained almost unchanged for more than 30 days in air;the emission peak position remained basically unchanged,the luminescent intensity remained above 85%for 10 days in water.In addition,these new perovskite-EP composites exhibit tensile and flexural properties due to the incorporation of flexible epoxy resin,which can be well applied to the fields of flexible luminescent devices and optical functional materials.Perovskite-PMMA composites were successfully prepared by solvent evaporation.Solid granular PMMA was dissolved in toluene solvent,and then mixed with perovskite quantum dot toluene solution.After dropping on quartz substrates,transparent sheet composites were obtained after toluene was completely volatilized.In the whole preparation process,no chemical reagents were involved except the introduction of toluene solvent with weak polarity,which guaranteed the luminescence color and intensity of perovskite quantum dots to a certain extent.The whole process was completed under room temperature and avoided the influence of light and heat on perovskite quantum dots.The luminescent color and emission peak position of the prepared composite material are consistent with the initial perovskite quantum dots.After40 days in air,the emission peak position and luminescent intensity of the sample remain almost unchanged.After 30 days immersion in water,the luminescent intensity can still maintain more than 80%of the initial value,which proves that the sample has strong stability.