The unique structure of zero-dimensional (0D) perovskite-analogues has attracted a great amount of research interest in recent years. To date, the current compositional library of 0D perovskites is largely limited to the lead-based Cs 4 PbX 6 (X = Cl, Br, and I) systems. In this work, we report a new synthesis of lead-free 0D Cs 3 BiX 6 (X = Cl, Br) perovskite-analogue nanocrystals (NCs) with a uniform cubic shape. We observe a broad photoluminescence peak centered at 390 nm for the 0D Cs 3 BiCl 6 NCs at low temperatures. This feature originates from a self-trapped exciton mechanism. In situ thermal stability studies show that Cs 3 BiX 6 NCs remain stable upon heating up to 200 °C without crystal structural degradation. Moreover, we demonstrate that the Cs 3 BiX 6 NCs can transform into other bismuth-based perovskite-analogues via facile anion exchange or metal ion insertion reactions. Our study presented here offers the opportunity for further understanding of the structure-property relationship of 0D perovskite-analogue materials, leading toward their future optoelectronic applications.

In this work, an octagonal Penrose-type photonic quasi-crystal fiber (PQF) with dual-cladding is proposed. By optimizing three geometric degrees of freedom, the PQF exhibits ultra-flattened near-zero dispersion of 0.014±0.293  ps/nm/km, ultra-low order confinement loss of 10 dB/km, and large effective mode area of over 16.2  μm in a broadband of wavelength from 1.27 to 1.67 μm, covering almost all optical communication bands. At the common communication wavelength 1.55 μm, completely opposite trends of the dispersion and the confinement loss varying with the air-filling factor in the inner cladding are demonstrated. In addition, the robustness of optical properties including dispersion, confinement loss, and effective mode area in this PQF is discussed, assuming a deviation ±3% of all air holes.

We report a correlation between the structural phase transition of CsPbX₃ (X=Cl, Br, I) nanocrystals (NCs) and their temperature dependent steady-state photoluminescence (PL) and time-resolved PL (TRPL). In contrast to...