The Stability Enhancement And Luminescence Regulation Of Cesium Lead Halogen Perovskite Quantum Dots

With the rapid development of science and technology,the information technology industry is constantly updated and improved.Due to its low price,easy band gap adjustment,wide absorption spectrum,narrow emission spectrum,and high quantum yield,all-inorganic lead halogen perovskite quantum dots（Cs Pb X₃ QDs）have aroused tremendous interest in photoelectric device,biological imaging,solar cells,laser technology and other fields.Although the studies on all-inorganic lead halogen perovskite are developing vigorously in recent years,there are still some problems to be solved urgently.Firstly,due to the serious anion exchange between halogen atoms,all-inorganic Cs Pb X₃ QDs can hardly emit white light.Secondly,due to the essential characteristics of ionic crystals,the shortcomings of perovskite quantum dots are not stable enough.They are easily affected by air and water and cause deterioration,which has strict requirements on the preservation environment.Finally,lead,as a toxic element,also limits the use of perovskite quantum dots.Therefore,the preparation of perovskite quantum dot materials with high photoluminescence intensity,low toxicity and high stability is still a hot research issue at present,and there are still unresolved problems that need to be further studied.Graphite carbon nitride quantum dots（CNQDs）,as carbon-based materials,have stable structure and luminescence properties.The raw materials needed for its preparation are easy to obtain,the price is relatively cheap,and the preparation process is correspondingly simple,which can be produced on a large scale.The CNQDs prepared by oxidation have good stability and various functional groups on the surface,which provides a possibility for the regulation of the stability and optical properties of perovskite quantum dots based on CNQDs.This paper focuses on how to improve the photoluminescence（PL）intensity and stability of perovskite quantum dots.The specific research contents are as follows:In this paper,cesium oleate was injected into Pb X₂ solution by thermal injection method to prepare Cs Pb X₃ QDs（X is Cl,Br,I）.On the other hand,this work improves the repair degree of surface defects of perovskite quantum dot by mixing perovskite quantum dot material with CNQDs which are semiconductor materials without metal,and then improves the photoluminescence intensity of the material.At the same time,the stability of all-inorganic cesium lead chloride perovskite quantum dots（Cs Pb Cl₃QDs）and cesium lead bromoperovskite quantum dots（Cs Pb Br₃ QDs）has been greatly enhanced.In this paper,the effects of mixing CNQDs with Cs Pb X₃ QDs on the PL properties and stability of the materials are introduced in detail.The morphology and structure of the sample were characterized by transmission electron microscope.The results showed that the samples had good crystallinity,and the CNQDs were not doped or recombined with perovskite quantum dots,which was also verified by X-ray electron energy spectrum analysis.The photoluminescence spectra of each sample were measured by fluorescence spectrophotometer.The experimental results show that the addition of CNQDs can enhance the fluorescence intensity of Cs Pb X₃ QDs in a period of time,and the stability of cesium lead bromo perovskite quantum dots（Cs Pb Br₃QDs）is improved as well as the fluorescence enhancement.Using the UV-Vis spectrophotometer to record the UV-visible absorption spectrum of samples.Spectral analysis showed that the fluorescence enhancement of the samples was not caused by the enhancement of light absorption,which is consistent with the light absorption phenomenon of perovskite quantum dots after surface defects were repaired reported in literatures.Since surface defects of perovskite quantum dot have been fixed,the samples produced a stronger fluorescence,which was further verified by the fluorescence lifetime test results of the samples.