Green-emitting Cs_(4)PbBr_(6) nanocrystals were synthesized by the water-assisted solid-state reaction method for the first time.Although CsPbBr_(3) phases were observed in the X-ray diffraction (XRD) patterns of the ...Green-emitting Cs_(4)PbBr_(6) nanocrystals were synthesized by the water-assisted solid-state reaction method for the first time.Although CsPbBr_(3) phases were observed in the X-ray diffraction (XRD) patterns of the perovskite nanocrystal samples as impurities,the XRD patterns of the samples could be well indexed to the trigonal Cs_(4)PbBr_(6) structure.The Cs_(4)PbBr_(6) perovskite nanocrystals showed a bright green emission with a narrow emission band centered at 518 nm with a full width at half-maximum of 26 nm.The photoluminescence quantum yield (PLQY) of the Cs_(4)PbBr_(6) nanocrystals was 36.8%.The Cs_(4)PbBr_(6) nanocrystal powder showed excellent durability at 85℃ and 85% humidity for 24 h,and retained 82% of the initial PL intensity.The Cs_(4)PbBr_(6) nanocrystal film light-emitting diode chip showed a luminous efficacy of 30.6 lm W_(rad)^(−1).展开更多
Zero-dimensional(0D)metal halides have received significant attention in recent years due to their attractive light-emitting properties derived from the presence of isolated building units.Here we report the synthesis...Zero-dimensional(0D)metal halides have received significant attention in recent years due to their attractive light-emitting properties derived from the presence of isolated building units.Here we report the synthesis,crystal structures,and linear optical and phonon properties of three newcomers to the family of 0D lead halides-Cs_(2)MHy_(2)PbBr_(6),Cs_(2)MHy_(2)PbI_(6) and Cs_(2)MHy_(2)PbBr_(3)I_(3)(MHy+=methylhydrazinium)which are the first examples of 0D lead halides with mixed cations.These compounds crystallize in the orthorhombic Cmce structure with isolated PbX_(6)^(4-)octahedral units and statistically disordered MHy+cations.X-ray diffraction revealed the selective substitution of halide ions in Cs_(2)MHy_(2)PbBr_(3)I_(3) with Br-occupying the positions of ions acting as hydrogen-bond(HB)acceptors and I-occupying non-interacting sites.This preferential occupation leads to a giant increase of the octahedral distortion(27-and 249-fold,compared to the bromide and iodide,respectively).Raman spectra confirm the static disorder of MHy+and preferential occupation of halide sites.With the use of linear optical measurements,we demonstrate that all compounds exhibit broadband orange-yellow emission attributed to self-trapped excitons(STEs).The observed Stokes shifts of Cs_(2)MHy_(2)PbBr_(6) and Cs_(2)MHy_(2)PbBr_(3)I_(3) are record large among 0D lead halides.A large increase of the octahedral distortion due to the preferential occupation of halide sites in Cs_(2)MHy_(2)PbBr_(3)I_(3) is reflected in the spectra by broadening and red-shift of its emission.This study paves the way for developing a new class of light-emitting 0D lead halides by synthesizing mixed-cation analogues.展开更多
基金supported by the Ministry of Trade,Industry and Energy(MOTIE)and the Korea Institute for Advancement of Technology(KIAT)through the International Cooperative R&D program(P0006844_Development of color conversion nanocrystal luminescence materials for next generation display).
文摘Green-emitting Cs_(4)PbBr_(6) nanocrystals were synthesized by the water-assisted solid-state reaction method for the first time.Although CsPbBr_(3) phases were observed in the X-ray diffraction (XRD) patterns of the perovskite nanocrystal samples as impurities,the XRD patterns of the samples could be well indexed to the trigonal Cs_(4)PbBr_(6) structure.The Cs_(4)PbBr_(6) perovskite nanocrystals showed a bright green emission with a narrow emission band centered at 518 nm with a full width at half-maximum of 26 nm.The photoluminescence quantum yield (PLQY) of the Cs_(4)PbBr_(6) nanocrystals was 36.8%.The Cs_(4)PbBr_(6) nanocrystal powder showed excellent durability at 85℃ and 85% humidity for 24 h,and retained 82% of the initial PL intensity.The Cs_(4)PbBr_(6) nanocrystal film light-emitting diode chip showed a luminous efficacy of 30.6 lm W_(rad)^(−1).
基金supported by the National Science Center(Narodowe Centrum Nauki)in Poland under project no.2019/35/B/ST5/00043.
文摘Zero-dimensional(0D)metal halides have received significant attention in recent years due to their attractive light-emitting properties derived from the presence of isolated building units.Here we report the synthesis,crystal structures,and linear optical and phonon properties of three newcomers to the family of 0D lead halides-Cs_(2)MHy_(2)PbBr_(6),Cs_(2)MHy_(2)PbI_(6) and Cs_(2)MHy_(2)PbBr_(3)I_(3)(MHy+=methylhydrazinium)which are the first examples of 0D lead halides with mixed cations.These compounds crystallize in the orthorhombic Cmce structure with isolated PbX_(6)^(4-)octahedral units and statistically disordered MHy+cations.X-ray diffraction revealed the selective substitution of halide ions in Cs_(2)MHy_(2)PbBr_(3)I_(3) with Br-occupying the positions of ions acting as hydrogen-bond(HB)acceptors and I-occupying non-interacting sites.This preferential occupation leads to a giant increase of the octahedral distortion(27-and 249-fold,compared to the bromide and iodide,respectively).Raman spectra confirm the static disorder of MHy+and preferential occupation of halide sites.With the use of linear optical measurements,we demonstrate that all compounds exhibit broadband orange-yellow emission attributed to self-trapped excitons(STEs).The observed Stokes shifts of Cs_(2)MHy_(2)PbBr_(6) and Cs_(2)MHy_(2)PbBr_(3)I_(3) are record large among 0D lead halides.A large increase of the octahedral distortion due to the preferential occupation of halide sites in Cs_(2)MHy_(2)PbBr_(3)I_(3) is reflected in the spectra by broadening and red-shift of its emission.This study paves the way for developing a new class of light-emitting 0D lead halides by synthesizing mixed-cation analogues.
