Preparation And Optical Properties Of Nd Doped Blue Perovskite Quantum Dots

The caesium lead halide perovskite quantum dots with ABX₃（A=Cs,B=Pb,X=Br,Cl or I）structure prepared by colloidal chemistry method have nearly 100%photoluminescence quantum yield（PLQY）and small emission half peak width.The emission wavelength of Cs Pb X₃（X=Br,Clå’ŒI）perovskite quantum dots can cover the whole visible light band by adjusting the optical band gap through halogen ion exchange.The photoluminescence quantum yield of Cs Pb X₃（X=Br,Cl and I）perovskite quantum dots is higher than 90%in the green and red region.These advantages make it have broad application potential in light-emitting diodes,lasers,solar cells and photodetectors.However,compared with the green and red quantum dots,the PLQY of the intrinsic blue perovskite quantum dots is very low,which requires B-site cation doping to improve the fluorescence properties and stability.In this paper,we use the co-doping of Nd³⁺and halogen ions to obtain bright blue quantum dots,and study the doping effect of Nd³⁺in blue quantum dots.Nd³⁺-doped blue quantum dots were synthesized by hot injection method and ion exchange color mixing method,respectively.The doping effects of the two methods were compared,and the realization mechanism of doping was discussed.The main contents are as follows:（1）Nd³⁺-doped CsPb（Cl/Br）₃ blue perovskite quantum dots were prepared by hot injection method with different stoichiometry.Compared with the undoped QDs,the PLQY of the QDs doped with Nd³⁺is significantly improved.The PLQY of the QDs with emission peaks at 456 nm and 489 nm reaches 60%and 70%respectively.In addition,compared with the 489 nm quantum dots,the fluorescence properties and stability of the quantum dots with the emission peak at 456 nm are improved significantly.XPS results show that the hot injection method needs higher Nd³⁺-doping concentration to effectively improve the performance and stability of QDs.（2）Furthermore,the intermediate of Cs₃NdCl₆ quantum dots was prepared by thermal implantation.The dissociation of Cs₃NdCl₆ quantum dots and the formation of Cs Pb（Cl/Br）₃ quantum dots were realized by ion exchange between Cs₃NdCl₆ quantum dots andCs Pb Br₃ quantum dots.This method is called room temperature ion exchange color mixing method.In addition,high quality blue perovskite quantum dots with emission wavelengths from 419 nm to 489 nm can be easily obtained by adjusting the mixing ratio of precursor quantum dots.The PL peak at 489 nm has 93%high PLQY.TEM results show that the shape of Cs₃NdCl₆ quantum dots is standard hexagonal,and the size distribution uniformity of Nd³⁺-doped blue quantum dots is greatly improved compared with that of pure Cs Pb Br₃.The photothermal stability of QDs prepared by room temperature ion-exchange color mixing method was proved to be excellent.XPS results show that the room temperature ion-exchange color mixing method can effectively improve the performance and stability of QDs at low Nd³⁺doping concentration.