In Situ Precipitation Of CsPbBr₃ Perovskite Quantum Dots From Borosilicate Glass And Its Structure-activity Control Mechanism

Luminescent materials are widely used in the field of optoelectronics.They play an im-portant role in our social development,and directly affect our daily lives.The quality of lumi-nescent materials is particularly important,which depends on some key factors,including quantum yield,optical purity and spectral stability.The cesium lead halide perovskite(Cs Pb X₃,X=Cl,Br,I)quantum dot material has excellent optoelectronic properties.It has a nar-row-band emission spectrum,a high photoluminescence quantum yield,and a full-spectrum adjustable.Therefore,it has become a popular material that has been widely studied in recent years,and has great potential in solar cells,LED lighting,and laser applications.Perovskite quantum dot materials have the characteristics of ionic crystals,and the crystal structure is eas-ily damaged in a humid and high temperature environment.Therefore,its poor stability limits its wide application.The stability problem is an urgent problem for cesium lead halide perov-skite quantum dot materials.The glass matrix is considered as a good carrier.The glass is pre-pared by the high temperature melting method and the overall crystallization method enables the cesium lead halide perovskite quantum dots to crystallize in situ in the glass,which greatly improves the stability of the perovskite quantum dots.Therefore,we have adopted a high-temperature melting method for the preparation of perovskite quantum dot glass,and use structure-effect control strategies such as glass structure control and doping to achieve luminous tunability,and improve the photoluminescence intensity and stability of the material.It includes the following three parts:1.Glass structure regulation.The glass doped with Cs Pb Br₃ quantum dots was prepared by the conventional melt quenching process and subsequent heat treatment.The glass has good thermal stability and optical properties.A narrow visible photoluminescence emission band(508-528 nm)was observed.With the change of B₂O₃ concentration,the position of the emis-sion peak changed,and the emission intensity changed significantly.Transmission electron mi-croscopy shows that as the glass composition changes,the size and number of quantum dots also change.The photoluminescence decay time is about 39.73-8.39ns,and it decreases with the increase of the quantum dot size.With the decrease of B₂O₃ concentration,the network struc-ture of the glass shows a high aggregation state,which provides sufficient growth space for the quantum dots.It was found that the light emission of quantum dot glass can be controlled by changing the glass network structure.2.Ag nanoparticles doped.Cs Pb Br₃ perovskite quantum dot glass doped with Ag nanopar-ticles was prepared by conventional melt quenching process and subsequent heat treatment.Ag nanoparticles and Cs Pb Br₃ perovskite quantum dots coexisted in the TEM image of the glass sample.The emission spectrum shows that the photoluminescence intensity of the Ag₂O-doped sample with a molar ratio of 0.1%is 2.37 times that of the undoped sample.This enhancement of luminescence is generated by local surface plasmon resonance coupling between Ag nano-particles and Cs Pb Br₃ perovskite quantum dots.Ag₂O overdoping will weaken the photolumi-nescence intensity due to the plasmon resonance spectral self-absorption on the surface of Ag nanoparticles.Surface plasmon resonance self-absorption is detrimental to luminescence be-cause it increases the number of photo-generated charge carriers by non-radiative relaxation pathways.In addition,Ag nanoparticle-doped Cs Pb Br₃ perovskite quantum dot glass has excel-lent stability.The study of Ag nanoparticle-doped Cs Pb Br₃ perovskite quantum dot glass pro-vides new ideas for the future development of perovskite quantum dot photovoltaic devices.3.Alkali metal Li⁺doped.The Cs Pb Br₃ perovskite quantum dot glass prepared by a con-ventional melt quenching process and subsequent heat treatment.XRD and TEM proved that Cs Pb Br₃ perovskite quantum dots were successfully precipitated in situ in the glass matrix.It can be seen from the infrared spectroscopy that there is no significant change in the internal network structure of the glass.It is concluded that the doping of Li⁺has not caused a change in the glass structure and has not replaced the Cs lattice of the Cs Pb Br₃ quantum dots.As the amount of Li doped increases,both the photoluminescence intensity and the quantum yield in-crease.Further analysis of the fluorescence lifetime,with the increase of the introduced Li ions,the fluorescence lifetime showed an increase in the lifetime,indicating that the non-radiative transition decreased,and further proved that Li⁺doping may cause the surface defects of Cs P-b Br₃ perovskite quantum dots in glass to decrease.