The Study On Synthesis And Optical Properties Of Perovskite Nanocrystals With Controllable Size And Shape

With the development of research on nanomaterials,inorganic perovskite nanocrystals have gradually entered the field of visions.As an excellent nano-luminescent materials,its high fluorescence rate,ultra-low excitation power,ultra-wide,half-height full width,ultra-wide visible light emission band and other excellent luminescent properties have gradually become one of the most popular topics in nanomaterial researches.Inorganic perovskite nanocrystals,as a kind of luminescent material,it has gradually entered into the application and research of other optical devices and fields.In this paper,the synthesis and preparation of perovskite nanocrystals with different morphology,the construction of single quantum dot scanning system,the search of single quantum dots and the measurement of optical properties are discussed in details.As synthesis and preparation of perovskite nanocrystals with different morphologies,this paper mainly uses the method of colloidal chemical solution synthesis.The perovskite nanocrystals with different shapes and sizes are accurately synthesized by controlling the three main influencing factors,in order to fully reflect the quantum confinement effect of perovskite nanocrystals.The most advantageous advantage of the perovskite nanocrystals synthesized by the thermal injection method that the synthesis method is simple and easy to operate.The yield of the sample high and the cost is low.One of the main factors affecting the morphology and size of perovskite nanocrystals is temperature.The temperature affects the dissolution of the perovskite precursor and the separation of ions and molecules,and at the same time affects the nucleation rate and anisotropy of the perovskite nanocrystals.In this paper.the temperature adjustment of perovskite nanocrystals by thermal injection is from 80 degrees Celsius to 220 degrees Celsius.When the temperature is lower than 80 degrees Celsius,the reaction hardly proceeds.As the temperature increases,the rate of dissolution of various precursor drugs will be faster and faster,and the nucleation rate will be faster and faster too.The synthesis of nanocrystals gradually changes from anisotropic growth to isotropy growth.From eighty degrees to one hundred and twentydegrees,it is a square disc with a size of about 25 nm.one hundred and twenty to one hundred and fifty degrees,a spherical disc have formed a size of approximately 17 nm.When the temperature is higher than one hundred and fifty degrees Celsius,a three-dimensionally shaped nanocrystal is formed.And the size is gradually becoming smaller.When the temperature reaches 180 degrees,the size reaches a minimum of about 8 nm,and the shape is a cubic perovskite quantum dot.When the temperature continues to rise,the nucleation process is destroyed,the corresponding nanocrystal yield will decrease,the shape also tends to be irregular.The second factor affecting the nanomorphology of perovskite is the role of intermediate ligands.There are two kinds of intermediate ligands,one is organic acids such as acetic acid,caproic acid,oleic acid and so on.The difference is that the length of the carbon chain is different.There are also organic bases with these classifications ranging from two carbons to eighteen carbon chains.The relative proportion of the intermediate ligand organic acid and the organic base,and the type of the organic acid,that is the length of the carbon chain have an effect on the synthesis of the perovskite nanocrystals.The general rule is that the longer the carbon chain,the easier it is to form an isotropic nanocrystalline material,the size is getting smaller and smaller,and the shape tends to be regular.The third influencing factor is the type and relative proportion and amount of precursor.This factor is the greatest influence on the morphology of perovskite nanocrystals,which directly affects the nucleation and growth of perovskite nanocrystals.With regard to the construction of the optical system,under the premise of purchasing various single-item instruments,the self-construction and adjustment of the confocal single-molecule scanning system can be realized.Through the system with spectrometer,the lifetime,fluorescence flicker,spectrum of the single quantum dot nanocrystal and anti-bunching can be measured.The measurement of the optical properties of perovskite nanocrystals are focused on four directions.Firstly,perovskite nanocrystal fluorescent blinking was classified.Secondly,the fluorescence lifetime analysis of perovskite nanocrystals with different luminescence intensity was carried out.Through the lifetime distribution analysis and fluorescence lifetime index fitting,the possible luminescence channels of perovskite nanocrystals were obtained.Thirdly,an exciton composite channel model of single perovskite nanocrystals was proposed and compared with experimental values to obtain the mechanism of blinking.Fourthly,individual perovskite nanocrystal surface ligands and dangling bonds influence fluorescence blinking and single photon properties.