Design,Synthesis And Properties Of Perovskites Or Perovskite-like Halides Luminescent Materials

In recent years,perovskites or perovskite-like halides have launched a new paradigm in the area of solar cells,light emitting diodes,quantum dot light-emitting diodes,photodetectors,and so on.The luminescent properties of these materials depend not only on their unique crystal structure,but also on doped luminescent ions.Therefore,it is of great significance to explore the structural design strategies of novel perovskites or perovskite-like halides and to improve the luminescent properties by composition regulation and ion doping strategies.In this paper,three kinds of all-inorganic lead-free halide double perovskites Cs2AgInCl6,Cs2AgSbCl6 and Cs2NaBi1-xInxCl6,one lead-free perovskite derivative Cs2SnCl6-xBrx,and one zero-dimensional organic-inorganic metal halide(C9NH20)6Pb3Br12 were studied.And the design,synthesis and properties of these compounds are studied respectively.The main contents arc as follows:(1)The lead-free halide double perovskite Cs2AgInCl6 with high chemical and thermal stability have been prepared.By controlling the experimental conditions,the crystal sizes can be tuned from 5 ?m to 1.5 mm.Cs2zAgInCl6 is a direct band gap semiconductor with a wide band gap of 3.23 eV.The PL spectrum of Cs2AgInCl6 exhibits a broad red emission band peaking at 635 nm,which is attributed to the photo-inducced defects in Cs2AgInCl6.There is parity-forbidden optical transition in the band structure.And the optical band gap was determined to be 3.23 eV via the UV-vis measurement,while the band structure and optical absorption calculations verified that the evaluated band gap is 3.33 eV with a direct band gap showing good agreement.(2)The lead-free halide double perovskite Cs2AgSbCl6 have been prepared,which is an indirect band gap semiconductor and the material is found to have a varied band gap associated with different body colors.The anti-site defect model was established to investigate transposition influence on the optical and electronic properties of the double-perovskite Cs2AgSbCl6.By exchanging site-equal Ag and Sb ions,the two allotropes(an Ag atom makes atomic transposition with its nearest neighbor Sb atom and second-nearest neighbor Sb atom)are thermodynamically stable,and the band gap could be varied with relatively small lattice expansion.Cs2AgSbCl6 has a high decomposition temperature and is stable upon prolonged exposure to air and moisture.(3)The lead-free halide double perovskite Cs2NaBi1-xInxCl6:Mn2+ have been prepared.Depending on the manipulation of Bi3+/In3+ combination,the band gap increases with In3+ content,and a subsequent evolution from indirect to direct band gap is verified.First-principles calculations and parity analyses indicate a parity forbidden effect on Cs2NaInCl6,and a combination effect of absorption on Cs2NaBi1-xInxCl6 from both Cs2NaBiCl6 and Cs2NaInCl6.When doped with Mn2+,Cs2NaBi1-xInxCl6:Mn2+ yield a strong orange yellow emission except x=1.0.The associated Mn2+-doped photoluminescence depending on the Bi3+/In3+ substitution is also addressed from the variation of the different Mn-Cl environment and neighboring-cation effect.(4)Millimetre-sized defect perovskites Cs2SnCl6-xBrx have been prepared,with the body color continuously changing from transparent to yellow and finally to dark red.Using these lead-free single crystals as the photoactive materials in photodetectors,a narrowband photodetection model with a tunable response spectral profile from near violet to orange was fabricated.The narrowband photodetection is ascribed to the strong surface charge recombination-induced suppression of charge collection for short wavelength excitation.The low toxicity.high detectivity(2.71 ×1010 Jones),narrowband photodetection(FWHM?45 nm),and high ion diffusion barriers make the Cs2SnCl6-xBrx photodetector a promising candidate for more diverse applications.(5)A new single crystalline zero-dimensional(0D)organic-inorganic hybrid material(C9NH20)6Pb3Br12 has been prepared,where the face-sharing[PbBr6]octahedral isolated clusters[Pb2Br6-Pb1Br6-Pb2Br6]construct a 0D perovskite-like anionic framework.A broadband green emission peaking at about 522 nm was observed for this material,with a full width at half maximum(FWHM)of 134 nm,and a photoluminescence quantum efficiency(PLQE)of about 12%,which was attributed to radiative recombination of holes and electrons trapped at intrinsic vacancies as a new example in 0D metal halides.