Low-dimensional metal halides have recently attracted extensive attention owing to their unique structure and photoelectric properties.H erein, we report the colloidal synthesis of all-inorganic low-dimensional cesium copper halide nanocrystals (NCs) by adopting ah ot-injection approach.U sing the same reactants and ligands,b ut different reaction temperatures,b oth 1D CsCu 2 I 3 nanorods and 0D Cs 3 Cu 2 I 5 NCs can be prepared. Density functional theory indicates that the reduced dimensionality in 1D CsCu 2 I 3 compared to 0D Cs 3 Cu 2 I 5 makes the excitons more localized, which accounts for the strong emission of 0D Cs 3 Cu 2 I 5 NCs. Subsequent optical characterization reveals that the highly luminescent, strongly Stokes-shifted broadband emission of 0D Cs 3 Cu 2 I 5 NCs arises from the self-trapped excitons.O ur findings not only present am ethod to control the synthesis of low-dimensional cesium copper halide nanocrystals but also highlight the potential of 0D Cs 3 Cu 2 I 5 NCs in optoelectronics. Scheme 1. Colloidal synthesis of cesium copper halide nanocrystals.Supportinginformation and the ORCID identification number for one of the authors of this article can be found under: https://doi.

A series of lead‐free double perovskite nanocrystals (NCs) Cs2AgSb1−yBiyX6 (X: Br, Cl; 0≤y≤1) is synthesized. In particular, the Cs2AgSbBr6 NCs is a new double perovskite material that has not been reported for the bulk form. Mixed Ag–Sb/Bi NCs exhibit enhanced stability in colloidal solution compared to Ag–Bi or Ag–Sb NCs. Femtosecond transient absorption studies indicate the presence of two prominent fast trapping processes in the charge‐carrier relaxation. The two fast trapping processes are dominated by intrinsic self‐trapping (ca. 1–2 ps) arising from giant exciton–phonon coupling and surface‐defect trapping (ca. 50–100 ps). Slow hot‐carrier relaxation is observed at high pump fluence, and the possible mechanisms for the slow hot‐carrier relaxation are also discussed.

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