Optical Properties And Applications Of Rare Earth Doped All Inorganic Lead-halide Perovskite Quantum Dots

All-inorganic perovskite CsPbX₃?X=Cl,Br,I?quantum dot?QD?is a novel lead-halide perovskite quantum dot with large absorption cross section,narrow emission peak widths,high photoluminescence quantum yield?PLQY?,anion tunable absorption/emission wavelengths,simple preparation process and relatively stable crystal structure.It has broad application prospects in the field of new quantum dot lighting and display,and has become the frontier and focus of academic research in the field of optoelectronic materials and devices.However,the blue-violet light material represented by CsPbCl₃ QD has low PLQY,and the red light system represented by CsPbI₃ QD is extremely unstable,which limits their practical application and becomes a key problem to be solved urgently.Rare earth ions have abundant 4f-4f and 4f-5d transition levels,a wide range of emission wavelengths,a long PL lifetime,and extremely narrow emission peak.If the doping of rare earth ions into perovskite quantum dots is achieved,the optical properties of CsPbX₃ QD will be greatly improved and expanded,such as increasing the photoluminescence quantum efficiency?PLQY?of CsPbCl₃ QD,obtaining stable red emission,and expanding the adjustable wavelength range of CsPbX₃ QD to near-infrared and even middle-infrared regions,the single-phase perovskite QD emits white light or multi-color light and so on.In view of this,this thesis focuses on how to realize the effective doping and luminescence control of rare earth ions into perovskite quantum dots.The luminescence of rare earth doped perovskite QD was firstly realized and reported in the world.The specific work contents are as follows:?1?We have modified the traditional thermal injection method.By appropriately adjusting the addition order of the lanthanide chloride and synthetic temperature control,the lanthanide ions,such as Ce³⁺,Sm³⁺,Eu³⁺,Tb³⁺,Dy³⁺,Er³⁺and Yb³⁺,doped CsPbCl₃ QD was realized for the first time.The double emissions of excitons and rare earth ions are obtained in the doped perovskite QD,and the PLQY of rare earth ion doped CsPbCl₃ QD with visible emission such as Ce³⁺,Eu³⁺is increased from 5%to 20-30%.Yb³⁺doped QD has ²F_5/2-²F_7/2 infrared emission?1000-nm?and the exciton emission,and the total PLQY is up to 142%.?2?A series of ion-pairs(Ce³⁺/Mn²⁺,Ce³⁺/Eu³⁺,Ce³⁺/Sm³⁺,Bi³⁺/Eu³⁺and Bi³⁺/Sm³⁺)co-doped CsPbCl₃ QD white phosphors were prepared by modified hot-injection method,and then through typical anion exchange reaction,a series of ions pairs co-doped CsPbCl_xBr_3-x QD white phosphors with better color rendering index and higher luminous efficiency are obtained,and a series of white LED?WLED?devices were prepared.Among them,Ce³⁺/Mn²⁺co-doped CsPbCl_1.8Br_1.2perovskite QD has the highest efficiency,and the best PLQY reaches 75%.It was coated on a 365 nm UV chip to obtain a WLED device with a lumen efficiency of 51lm/W.?3?Design and preparation of metal chloride?YCl₃,LuCl₃,LaCl₃,ZnCl₂,CdCl₂and SnCl₂?doped CsPbI₃ QD,the doping significantly improved the PLQY of CsPbI₃ perovskite QD,from 51%to over 80%?MCl_x:PbI₂=0.12,x=2 or 3?.Among them,when YCl₃:PbI₂=0.12,the PLQY of QD can reach 91%.Moreover,the environmental storage time of CsPbI₃ perovskite QD has been greatly extended.The conversion of the black?phase to the yellow?phase occurred within 5 days of the undoped QD,and the CsPbI₃ QD after the introduction of the metal chloride hardly degraded in more than two months.This can be attributed to the fact that metal cations and Cl^-ions with smaller ionic radii are doped into the QD,resulting in a more stable crystal structure.Among them,when the amount of YCl₃ is 0.08g,CsPbI₃ nanorods are generated,and the emission peak position of the CsPbI₃nanorods is blue-shifted to 652 nm,which is blue-shifted by 50 nm with respect to that of undoped QD.This also demonstrates that the metal chloride doping mode can properly adjust the red light emission wavelength of the perovskite QD.?4?Ni-doped CsPbCl_xBr_3-x QD was successfully prepared by supersaturated recrystallization method at room temperature,achieving high-efficiency"healthy"blue light?450nm⁴80nm?emission,the optimal PLQY is as high as 87%,which is nearly three times the PLQY of QD without Ni doping?³0%?.Furthermore,the blue light LED device with 470 nm wavelength was successfully fabricated by using the classical blue LED structure?NiO_x as hole transport layer and TBPi as electron transport layer?,and the external quantum efficiency?EQE?was 2.4%,which is 24times that of an undoped QD LED device?0.1%?.