Synthesis And Luminescent Properties Of Highly Stable All-inorganic Perovskite Quantum Dots

Quantum dots（QDs）have a variety of luminescent materials.Some of the traditional II-VI and III-V groups have been commercially applied,but their synthesis process is complex and the cost is high.In contrast,the all-inorganic Cs Pb X₃（X=Cl,Br,I）QDs material has excellent photoelectric properties and good chemical processing properties,making it a hot spot of current extensive research,and is expected to be used in solar cells,light emitting diodes（LED）,photodetectors and other fields.Cubic phase red perovskite with narrow band gap（1.73 e V）defect tolerance（α-Cs Pb I₃）is one of the most excellent materials recently proved to have outstanding performance for high-efficiency luminescence,X-ray detection and photovoltaic devices.Unfortunately,these halide perovskites are prone to cubic phase（α-phase）to orthogonal phase（δ-phase）,which may be related to their high ionic properties,metastable structure and photodegradation caused by imperfect surface passivation.This chemical instability is one of the main obstacles to its further commercial application.In order to overcome this shortcoming,people are committed to exploring new synthetic methods and understanding the chemistry reaction of stableα-Cs Pb I₃.Therefore,this study takes the all-inorganic Cs Pb I₃ QDs as the research object.By optimizing the crystal surface state,the crystal quality is improved,achieving gains in luminous efficiency and stability of QDs,thereby meeting the requirements of practical applications.The relevant research content and results are as follows:（1）By using the ion exchange method,three fluorine-containing metal inorganic salts（Na F,Zn F₂·4H₂O and Sn F₂）are selected to improve stability ofα-Cs Pb I₃ QDs and passivation of surface defects.The double-exponential fitting fluorescence lifetime of ZF-Cs Pb I₃ QDs obtained after the introduction of Zn F₂·4H₂O increases from 37.12 ns to 43.31 ns,and the radiation recombination lifetimeτ₂ is also increased accordingly,indicating that fluoride ions passivate surface defects and inhibit their nonradiative transitions.At last,the stability of the material was compared and verified.ZF-Cs Pb I₃ QDs could keep in the air for 5 days without phase change,which confirmed that fluoride ion passivation crystal surface can be used to enhance the stability of QDs.（2）Based on injection method,an iodine rich synthesis route was developed by introducing excess Zn I₂ for the preparation of high crystal qualityα-Cs Pb I₃ QDs.The photoluminescence quantum yield of QDs has been increased to 99%.At the same time,due to the reduction of surface vacancy defects,the fluorescence lifetime changes from double exponential decay to single exponential decay,and the fitting lifetime is 14.47 ns.The results show that the prepared Rich-Cs Pb I₃ QDs have good photostability,polar solvent resistance,photoluminescence thermal stability and long-term storage stability in air,and can be stored in air for more than 30 days.This study is to prepare stableα-Cs Pb I₃ QDs provide a new way to be applied in the fields of photocatalysis and photoelectricity.