Optimization And Tuning The Optical Properties Of Zero-dimensional Lead-free Metal Halides By Doping

The zero-dimensional metal halides（0D MHs）retain the photophysical properties of individual metal halide octahedra or metal halide clusters.Strong quantum confinement effects and softer lattices give these materials self-trapped exciton（STEs）broadband emission accompanied by large Stokes shifts and high Photoluminescence Quantum Yield,which have advantages for application in white light emitting diodes（LED）.To design and synthesize 0D MHs with excellent optical properties,one strategy is to use metal halide polyhedra with intrinsic luminescence as inorganic units.Another strategy is host-guest doping,which can optimize the optical properties of the host material or introduce new luminescent centers.In doped materials,the structure and stability of the material are mainly determined by the host material,while the optical properties are mainly determined by the dopant ions.Such a strategy can be used to achieve variable optical properties through the rational design of host and guest materials for single doping or co-doping.Currently,the reported luminescent 0D MHs have a single emission peak and their luminescent color is not easily tuned by external factors.Predictably,materials with tunable dual emission peaks will show great promise in the fields of fluorescence analysis,anti-counterfeiting,and sensors.Hence,our work synthesized Sb-and Mn-based 0D MHs with intrinsically luminescent.Then,two materials with double emission peaks were synthesized by doping,and their luminescent colors can be tuned by excitation wavelength or temperature.The main contents are as follows:1.We synthesized two 0D MHs（TPP）₂SbCl₅ and（TPP）₂MnCl₄ with efficient broadband luminescence peaks at 660 nm and 531nm,respectively.The luminescence of（TPP）₂SbCl₅ originates from the STEs emission induced by Jahn-Teller-like distortion during the excited state,while the luminescence of（TPP）₂MnCl₄ originates from the ⁴T₁ to⁶A₁ electron transition of the[MnCl₄]^2-tetrahedra.2.Based on the previous chapter,the optical properties of the two intrinsic materials provided guidance for Sb³⁺and Mn²⁺ions use as dopants.The optical properties of the host material（MXDA）₂CdCl₆ crystals are greatly optimized by the single doping of Sb³⁺or Mn²⁺ion.Since the luminescence between the isolated octahedra in the 0D metal halides is independent of each other,the single doped material shows one emission peak,while the co-doped material shows a double emission peak originating from two different luminescence centers([SbCl₆]^3-and[MnCl₆]^4-).After co-doping,the double emission can be modulated by changing the excitation wavelength.3.In view of the third chapter,simpler single doping of special ions with multiple STEs distortion modes can also be used to achieve double emission.Cu⁺doping greatly optimizes the optical properties of the host PZZnCl₄ and PZZn Br₄ materials,showing significant STEs emission.In contrast to the low-temperature PL spectra of PZZnCl₄:Cu⁺,which has a single emission peak,PZZn Br₄:Cu⁺has an apparent double emission peak.We found that with Cu⁺,a special doping ion,we can obtain temperature-dependent double-emission PL spectra and tunable luminescence colors by the unique multiple STEs energy level modes in its excited state.