Construction And Stability Enhancement Of Lead Halide Perovskite Quantum Dot Composite Luminescent Materials

In recent years,lead halide perovskite quantum dots have received widespread attention as a type of"star material".Because of its advantages such as long carrier diffusion length,high extinction coefficient and low defect density,it has a very broad application prospect in the optoelectronic fields such as light emitting diodes(LEDs),lasers,and photodetectors,and has become a new generation of solid-state lighting and display Cenozoic material.However,due to its structural instability,nano-scale effect,high surface energy,etc.,this material is sensitive to light,heat and humidity,has poor stability,and is limited in the field of optoelectronic applications.Therefore,improving the stability of Cs Pb X3(X=Cl,Br,I)is the most important task.The design of composite materials and the reduction of dimensions are very effective ways to improve its stability.Mineral materials have the characteristics of high stability,ion exchange,high specific surface and environmental friendliness.It can be used as the host material to accept a variety of guest materials to achieve the assembly of new functional materials.As mentioned before,the perovskite quantum dots are combined with mineral materials,and the performance of the two is combined to achieve performance control and coordinated improvement.A variety of new quantum dots and mineral composite materials have emerged,and their application fields are also constantly expanding.In addition,the stability of two-dimensional perovskite materials is better than that of perovskite quantum dots.By selecting different types of interlayer organic groups,the synthesis of new low-dimensional perovskite materials can achieve highly stable perovskite materials.Therefore,this paper intends to use different mineral materials to synergistically control the luminescence performance and stability of lead halide perovskite quantum dots,build a series of composite materials,and explore the application of perovskite quantum dot composite materials in white LED.The main research results of this paper are as follows:In this paper,a series of composite optical material systems are constructed by different mineral materials to synergistically regulate the luminescence performance and stability of lead-halogen perovskite quantum dots.And the application in white LEDs was explored.In addition,a new two-dimensional high-stability perovskite material was designed and synthesized to study its luminescent properties.The innovations of this paper are shown as follow:(1)Based on the excellent heat dissipation properties of the natural mineral halloysite nanotubes and two-dimensional boron nitride layered nanosheets,a series of perovskite quantum dots@mineral composite materials are designed and constructed.through electrostatic interaction and chemical bonding.An effective combination of quantum dots and minerals reveals the effect mechanism of stability improvement.It provides new ideas for optimizing the luminescence performance of perovskite quantum dot luminescent materials and improving their luminescence thermal stability.It has opened up new ways for a natural tubular and two-dimensional layered of minerals.(2)Based on the multi-stage pore structure of porous diatomite,a perovskite quantum dot and diatomite composite material is designed to enhance the luminous intensity and improve the thermal stability through the nano-cavity resonance of diatomite The luminous efficiency and thermal stability of mineral quantum dots have been enhanced.It brought new ideas and expanded the application fields of porous mineral materials.(3)Using organic amine as the organic layer and lead-bromine layer as the inorganic layer,a novel two-dimensional perovskite material(C8H12NO2)2Pb Br4 with n=1 is alternately synthesized,which has high stability and easy adjustment of optical properties.The main research results are summarized as follows:(1)One-dimensional Cs Pb Br3@HNTs composite material was constructed by one-step method.There is a large amount of positive charges on the outside surface of halloysite.Through electrostatic interaction,halogen anions are adsorbed in situ to form crystal seed.Then the Cs Pb Br3@HNTs composites are synthesized.By changing the halloysite load volumes,halloysite nanotube length,and other conditions,the experiment was used to optimize the preparation process to determine the optimal preparation process route and experimental parameters.The research on the thermal stability of Cs Pb Br3@HNTs composites was discussed.Since HNTs has a hollow nanotube structure,the luminous intensity of the Cs Pb Br3@HNTs composite is about 80%of the initial intensity when the temperature is heated to 100 ~oC.The excellent thermal stability should be attributed to the high thermal conductivity of alumina in HNT and the increased heat dissipation area due to the hollow tubular structure of HNTs.In addition,the composite material has excellent light-induced stability under ultraviolet radiation and storage stability in a humid environment.(2)CPX-DE-g-PAA composite was constructed by grafting polymerization.A diatomite mineral with light-enhanced quasi-photonic crystal structure was selected to construct a polyacrylic acid-grafted diatomite(DE-g-PAA)media reactor for in-situ capture of perovskite quantum dots(Cs Pb X3,X=Cl,Br,I).The results characterization verify that the cavity structure of the multi-stage channel can perform the grafting reaction more effectively.In addition,-COOH captured in DE-g-PAA can be used as a surface ligand in the synthesis of perovskite quantum dots.Instead of traditional oleic acid,perovskite nanocrystals can be evenly rivetted in the cavity and the surface.The constructed polymer brush provides an encapsulating protective layer for the perovskite quantum dots.Secondly,CPB-DE-g-PAA composites can improve both thermal stability and water resistance while also improving their luminous efficiency.The luminous efficiency of the composite material was increased to more than twice that of the original CPB,reaching 76.4%.The prepared CPB-DE-g-PAA composite material not only maintains a high photoluminescence quantum yield,but also exhibits excellent thermal stability and water resistance.Incredibly,after the introduction of light-enhanced quasi-photonic crystal diatomaceous,the luminescent thermal quenching of CPB-DE-g-PAA was significantly suppressed,and the initial intensity of?73%was still maintained at373 K.The results show that the introduction of diatomite can significantly enhance the heat resistance of CPB-DE-g-PAA;at the same time,the CPB-DE-g-PAA film exhibits a strong green light emission after soaking in water for 120 hours,approximately 13 times of pure CPB QDs film(about 9 hours).Finally,the electromagnetic field intensity distribution of CPB-DE-g-PAA composites with different cavity diameters was calculated for the first time,using finite-difference time-domain method(FDTD).The improvement in luminescence should be attributed to the electromagnetic field enhancement caused by the diatomite cavity resonance effect simulated by FDTD.(3)Construction of two-dimensional CPX@BN composite materials.Composite construction of lead halide perovskite quantum dots and two-dimensional materials.First,two-dimensional(2D)hexagonal boron nitride was stripped to prepare nanosheets.Through a large number of experimental conditions,the optimal stripping time was first determined,and a good stripping effect was obtained.A 50-nm-thick BN nanosheet stack was obtained.Then,the perovskite nanocrystals were uniformly grown in situ by a one-step method.After being functionalized with the amino group,the perovskite quantum dots were rivetted on the stripped BN nanosheets to form a stable CPX@BN-E.CPX@BN(X=Cl,Br,I)nanocomposites can improve thermal stability.CPX@BN-E composites have excellent thermal stability due to the introduction of high thermal conductivity BN.The PL intensity at 120~oC remains at 80%of its initial strength at RT,which is the highest thermal stability ever reported for an inorganic composite based on all inorganic lead halide perovskite materials.At the same time,the mechanism of improving thermal stability was also discussed.(4)Synthesis of two-dimensional(C8H12NO2)2Pb Br4 hybrid perovskite materialAn attempt was made to synthesize a new 2D structural material.(C8H12NO2)2Pb Br4was synthesized using dopamine as the organic interlayer group and the lead-bromine octahedron layer as the inorganic layer.It has novel narrow-band blue light emission and high stability.By doping manganese ions,blue and orange red light emission,band edge emission of hybrid perovskite materials,and T1-~6A1 energy transfer of manganese ions can be achieved.