The fascinating optoelectronic properties of semiconductor quantum dots (QDs) originate from the quantum confinement effect; i.e., the band gap increases as the size decreases. Another significant parameter dictating the photophysics of QD is the dynamics of trapping and detrapping from the trap-states, but it is nonetheless less understood. To understand these aspects, herein we investigate the photoluminescence (PL) fluctuations in CdSe QDs using time-resolved PL spectroscopy by systematically varying its core size, maintaining a constant shell thickness by coating with CdS followed by ZnS. The probability density distribution of ON- and OFF-events of QDs is constructed from the PL trajectories and fitted with the truncated power-law from which the trapping (k t) and detrapping (k d) rate constants are estimated. The increase in φPL observed with the increase in core size of CdSe at the ensemble level is related to the enhanced k d/k t and charge carrier wave function localization in the core. Indeed, the band gap decreases as the core size increases, bringing the trap-states close to the band edge positions, leading to an efficient detrapping of carriers. The fluorescence lifetime-intensity distribution plots revealed the presence of a high-intensity and high-lifetime component due to neutral exciton recombination and a low-intensity and low-lifetime component due to trap-induced Auger recombination. The decay kinetics in a single QD is further modeled using a pre-equilibrium approximation.

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The design of cube-connected nanorods is accomplished by connecting seed nanocrystals of a defined shape in a particular orientation or by etching selective facets of preformed nanorods. In lead halide perovskite nanostructures, which retain mostly a hexahedron cube shape, such patterned nanorods can be designed with the anisotropic direction along the edge, vertex, or facet of seed cubes. Combining the Cs-sublattice platform for transforming metal halides to halide perovskites with facet-specific ligand binding chemistry, herein, vertex-oriented patterning of nanocubes in one-dimensional (1D) rod structures is reported. By tuning the length of host metal halides, their lengths could also be tuned from 100 nm to nearly 1000 nm. The symmetry of the hexagonal phase of host halide CsCdBr 3 and product orthorhombic CsPbBr 3 helped in maintaining the vertex [201] as the anisotropic direction. Neutral exciton recombination rates, extracted from photoluminescence blinking traces, showed a systematic increase from isolated cubes to cube-connected nanorods of various lengths. Efficient coupling of wave functions in vertex-oriented cube assemblies permits exciton delocalization. Our findings on carrier delocalization in cube-connected nanorods along their vertex direction having minimum interfacial contacts provide valuable insights into the fundamental chemistry of assembling anisotropic halide perovskite nanostructures as conducting wires.

The magnetic properties of Zintl phase barium vanadium selenide (BaVSe3) were investigated experimentally and theoretically.