Synthesis And Luminescence Tuning Of Doped Inorganic Lead-Free Perovskite-type Nanocrystals

Lead-based perovskite nanocrystals(NCs),attributed to their excellent optoelectronic properties and solution-processing advantages,have emerged as one of the most potential optoelectronic materials and attracted great attention in recent years.However,they possess poor stability and lead toxicity.Therefore,it is urgent to develop more stable lead-free perovskites with comparable optoelectronic properties.To achieve efficient and tunable luminescence for lead-free perovskite NCs,study on structural design,composition regulation and ion doping of lead-free perovskite NCs is of great significance.This research takes Cs2AgInCl6 and Cs2ZrCl6 as the lead-free perovskite nanocrystal matrixes.To improve their optical properties,synthesis optimization,composition regulation and ion doping(including Bi3+,Sb3+and rare earth ions)strategy were studied in detail.The research will be shown as the following parts:(1)A feasible synthesis method of lead-free double perovskite Cs2AgInCl6 NCs is proposed.Bi3+doped Cs2AgInCl6 NCs were synthesized by high temperature hot injection method with less-toxic precursors.Through the optimization of synthesis conditions(including temperature,ligands and precursors),the photoluminescence quantum yield of Cs2AgInCl6:Bi NCs with broadband orange emission peaked at 580 nm was improved by one order of magnitude.And the luminescence mechanism was also discussed.(2)Bi3+and Tb3+ions codoped Cs2AgInCl6 NCs were synthesized.Crystallographic characterization and theoretical calculations analysis proved that the dopant Tb3+ions occupied In3+sites in Cs2AgInCl6 lattice.With Bi3+ doping,the characteristic emission of Tb3+ could be excited by a new excitation peak(368 nm).By adjusting the doping concentration of Tb3+ions,Bi3+/Tb3+ codoped Cs2AgInCl6 NCs achieved tunable emission from green to orange through an energy transfer channel from self-trapped excitons to Tb3+ions.(3)Tunable luminescence of Cs2AgInCl6 NCs by rare earth Dy3+,Sm3+ and Tb3+ions doping was designed and realized.It was found that the dopant Dy3+,Sm3+ and Tb3+ ions occupied In3+ sites in Cs2AgInCl6 lattice.The introduction of rare earth ions endows Cs2AgInCl6 NCs with multiple emissions.With Sm3+ and Tb3+ions codoping,Cs2AgInCl6:Sm3+,Tb3+NCs realized tunable emission through an energy transfer channel between rare earth ions.A fluorescent pattern from the Bi doped Cs2AgInCl6:Sm3+,Tb3+NCs-hexane inks by spraying was made to show its potential application in fluorescent signs and anticounterfeiting technology.(4)Sb3+doped vacancy-ordered double perovskite Cs2ZrCl6 NCs were designed and synthesized.It was found that dopant Sb3+ions occupied Zr4+sites in Cs2ZrCl6 lattice.Under 250 nm excitation,Cs2ZrCl6:Sb3+NCs exhibited broadband emission at 470 nm and 620 nm,corresponding to the STEs emission and Sb3+emission,respectively.The white light emission from a single component system excited by 317 nm was achieved by adjusting the doping concentration of Sb3+in Cs2ZrCl6.