Study On Preparation,Stability Enhancement And Light-Emitting Device Of All Inorganic Lead Halide Perovskite Composites

The all-inorganic lead halide perovskite with many excellent photoelectric properties such as long carrier life,high charge carrier mobility,easily adjustable band gap,high photoluminescence quantum efficiency(PL QY)etc.has been widely concerned by researchers,which has broad application prospects in many fields of advanced optoelectronic devices.However,due to their inherent ionic crystal properties and weak resistance to the external interference,these shortcomings led to the unstable structure and luminescence of lead halide perovskites,limiting their further development.In view of this,improving the stability and luminescent properties of perovskite materials is an important and urgently solved issue.From the perspective of improving the stability of all-inorganic lead-halogen perovskite quantum dots(CsPbX3 PQDs,X=Cl,Br,I),the current paper used an inorganic,organic and combined composite matrix to achieve effective encapsulation of PQDs.The structure and optical properties of composites were optimized by designing systems and regulating reaction strategies.,we have successfully achieved a significant improvement in the stability of all-inorganic perovskite materials by protective structure.The main research contents of the paper are as follows:(1)By simply adding tetramethoxysilane(TMOS)into the CsPbX3 PQDs(X=Br,I and its mixture)optimized by tri-n-octylphosphate(TOP),CsPbX3 PQDs encapsulated by SiO2 was obtained under the relative humidity(RH)of 80%.The composite not only shows excellent optical properties,similarly to CsPbBr3 PQDs,but also possesses good air storage and thermal stability.The composites with different halogens can still maintain their original PL performance without anion exchange reaction.Furthermore,a phosphor-type light-emitting diode(LED)was constructed by using CsPbBr3 PQDs@SiO2 and CsPbBr0.6I2.4 PQDs@SiO2 as the green and red light-emitting layer,combined with commercial GaN chip.The green and red luminescence of this device showed the color saturation of 97%and 96.3%,respectively.It exhibited a wider color gamut than the National Television Standards Committee(NTSC)standard.Finally,a standard white light-emitting diode(WLED)with a color coordinate of(0.31,0.33),color temperature of 6386 K and a power efficiency of 30.7 lm/W was prepared by mixing CsPbBr3 PQDs@SiO2 with K2SiF6:Mn4+(KSF)powder.(2)A new strategy of encapsulating CsPbBr3 PQDs into polydiphenylvinylphosphine-styrene(PDPEP-co-S)based on one-pot heat injection method is proposed.Unlike conventional thermal polymerization,no polar solvent was introduced during the preparation of the composites,and the PQDs embedded in the PDPEP-co-S are monodispersed.The PL QY can be significantly improved from 39%to 90%after CsPbBr3 PQDs optimized by PDPEP-co-S,we found that multidentate ligand copolymer regarded as the encapsulated matrix by theoretical calculations and simulations can effectively limit charge transfer and passivate the surface defects of PQDs,thereby improving the PL QY.On this basis,we constructed a fluorescence emission model of this composites and studied the internal carrier dynamics in detail.In addition,composite possesses good long-term stability to external caustic environments such as water,methanol and ultraviolet light,which is great significance for practical application.Meanwhile,the embedded CsPbBr3 PQDs are easily released from the copolymer matrix by proper polar solvent treatment,which can reuse CsPbX3 PQDs and reduces environmental pollution.Finally,we successfully prepared WLED with a power efficiency of 90 1m/W based on this composite with high brightness.(3)PQDs were embedded in porous polystyrene microspheres(MPMs),and then silica shell was formed by the hydrolysis of octadecyltrimethoxysilane(OTMS),CsPbX3 PQDs/MPMs@SiO2 hybrid luminescent microspheres were obtained.Compared with the single organic/inorganic encapsulation,the stability of the luminescent microspheres has been further improved,which also shows up to PL QY of 84%.It is attributed to the fact that the MPMs@SiO2 shell effectively cuts off the direct contact between the external erosion environment and the internal embedded PQDs.The hybrid microspheres are modified with ultra-long alkyl chains,improving the ability of the composite to resist corrosion of solvent and heat.Therefore,these microspheres have good chemical/physical stability even when exposed to harsh environments(eg:deionized water,isopropanol,acid/alkali solutions,heating conditions,etc.).Especially,the water stability:the fluorescence intensity still maintains 48%of the initial fluorescence intensity for a 30-day storage period.Finally,WLEDs were fabricated by coating green hybrid microspheres and red commercial phosphors on GaN chips.The device exhibits a power efficiency of 81 1m/W and has good electroluminescence stability,indicating that the composite has certain application potential in the future lighting field.