Cyclodextrin-mediated Synthesis Of Colloidal CsPbX₃ Perovskite Nanocrystals

Metal halide perovskite(MHPs)have gained great attention as next-generation optoelectronic materials due to their excellent photophysical properties and a wide range of promising applications.In their production,storage and utilization,PNCs have been mostly adopted in the colloidal form.Organic molecules that could coordinate surface ions of perovskites are used as ligands to passivate and protect the luminescent nanocrystals.Commonly used in colloidal PNCs,oleic acid(OA)and oleylamine(OAm)are weakly bound to the perovskite crystal through hydrogen bonds and ion pairs.Such faint interactions make the interface of PNCs dynamic and unstable,bringing about the fast exchange and the easy loss of ligand molecules in the course of purification and storage.This results in the deterioration of optical properties,colloidal stabilities,and sometimes even structural integrity of PNCs.Hence,a judicious selection of strongly binding ligands should be exploited to overcome the stability problem and even improve the luminescence performance of colloidal PNCs.In this paper,the supramolecular?-cyclodextrin(?-CD)was introduced as the ligand of nano-perovskite in order to improve the fluorescence quantum efficiency and stability of colloidal PNCs in polar solvent.Perovskite nanosols with good properties were prepared by a simple and fast method using?-CD as the ligand.The main research contents are as follows:(1)In this work,cyclodextrins were used as a sole ligand to synthesize colloidal CsPbBr₃ PNCs using dichloromethane(DCM)-induced.The results show that the?-CD?DCM system has higher yield,higher luminescence quantum efficiency(PLQY),and better stability under water,heat and UV irradiation than the traditional OA/OAm ligands(OA/OAm)and toluene trigger.Strong interactions between CD hydroxyl groups and perovskite metal ions were revealed by X-ray photoelectron spectroscopy and Fourier transform infrared analysis.Using the non-toxic and low-cost ligand,this is the first report of a more economic and eco-friendly synthesis than ever for colloidal PNCs with high quality and stability.(2)CsPbBr₃ nanocrystalline colloid was synthesized by?-CD mediated by polar solvent ethanol(Et OH)induced.In this chapter,a greater exploration has been made on the previous basis,CsPbBr₃ nanocrystalline colloidal was prepared by using ethanol as a trigger solvent in consideration of the economy of raw materials,toxicity and properties of products.Finally,the characterization of PNCs was carried out by means of photoluminescence spectrum,UV-vis spectrum,X ray diffraction spectrum,X ray photoelectron spectrum and high power transmission electron microscope.The results showed that CsPbBr₃ nanosols were successfully prepared in ethanol,a highly polar solvent.The success of this experiment has broken the previous understanding that perovskite can not exist in a single ligand and strong polar environment,which will help to broaden the application range of CsPbBr₃.(3)The halogen ion exchange of?-CD@CsPbBr₃ nanocrystalline colloid was studied.In this paper,KI and Na Cl were used to provide halogen ions,and the prepared CsPbBr₃ nanometer perovskite was rapidly halogen ion exchange in ethanol solution,which could almost achieve tunable luminescence in the whole visible range,and the optical properties and stability of CsPbBr₃ were very good after halogen ion exchange.