Preparation And Optical,Opto-Electronic Properties Of Perovskite @MOF Composites

CsPbBr₃ quantum dots（QDs）are widely used on optoelectronics,light-emitting diodes（LED）,solar cells and other fields for its unique optical and electrical properties.Several factors hinder the application of perovskites and an important one is the poor stability.Researcher have made great effort to improve the stability of perovskites.We embed CsPbBr₃ QDs in metal organic frameworks（MOFs）to get stable compound materials.MOFs are organic-inorganic hybrid materials composed of metal nodes and organic ligands,which have high porosity and adjustable pore size.Zeolitic imidazolate frameworks（ZIFs）,a subclass of MOFs,have been considered as potential porous materials for encapsulating CsPbX3 QDs for their thermal and chemical stability,pore tunability,and rich topological diversity.We choose ZIF-8 as a promising candidate to incorporate with CsPbBr₃ QDs.The hybrid material has good stability（up to 3500 in N2）and excellent multiphoton excited photoluminescence.In this thesis,we have achieved the size and topology control of ZIF-8.We embed CsPbBr₃ QDs in ZIF-8 by different methods to investigate the properties of CsPbBr₃ QDs@ZIF-8 composite materials.The main research works are as follows.（1）Preparation of ZIF-8 and study of its properties.In this thesis,room temperature stirring method and solvothermal method were used to prepare ZIF-8 crystals,and a series of ZIF-8 crystals with different sizes were prepared.The crystal sizes ranging from 200 nm to 30 μm were changed by varying the ratio of Zn/2-mim（2-Methylimidazole）,the type of zinc source and the synthesis method.The results of SEM proved that the samples basically maintain the regular shape.The results of XRD patterns,XPS patterns and etc.showed similar properties.The optical and electrical measurements show that ZIF-8 has the characteristics of weak fluorescence and conductivity,and the peak of emission spectrum is around 485 nm.（2）Preparation of CsPbBr₃ QDs@ZIF-8 composites and studies of their optical and electrical properties.In this thesis,CsPbBr₃@ZIF-8 composites were synthesized by thermal evaporation,grinding and one-pot methods,which named as CsPbBr₃@ZIF-8-a,CsPbBr₃@ZIF-8-b,and CsPbBr₃@ZIF-8-c,respectively.The SEM,TEM,mapping,HRTEM,XRD and XPS patterns results demonstrate that the composites have the properties of both ZIF8 and CsPbBr₃,and the CsPbBr₃ QDs were successfully embedded in ZIF-8.The results of TGA and other tests show excellent thermal stability of the composites.The emission peaks of all three composites are near 520 nm,indicating a blue-shift compared to CsPbBr₃ QDs.We attribute the shift to size effect of the QDs.Notably,CsPbBr₃@ZIF-8-b exhibits five-photon absorption（5PA）and third harmonic generation（THG）under femtosecond laser,which shows promising applications in nonlinear optics.