We investigated the temperature-dependent photoluminescence (PL) properties of colloidal CsPbX 3 (X = Br, I, and mixed Br/I) quantum dot (QD) samples in the 30−290 K temperature range. Temperature-dependent PL experiments reveal thermal quenching of PL, blue shifting of optical band gaps, and line width broadening for all CsPbX 3 QD samples with increasing temperature. Interestingly, side-peak emissions that are spectrally separated from the excitonic PL peaks were observed for both CsPbBr 3 and CsPb(Br/I) 3 QD samples at temperatures below ∼250 K. The side-peak emission for the CsPbBr 3 QD sample is located at a lower energy compared to the band-edge peak, whereas that of the Br-rich CsPb(Br/I) 3 alloy QD sample is located at a higher energy than that of the band-edge peak. We found that the CsPbBr 3 QDs have two emissive states, a band-edge state, and one involving shallow defects, which can be spectrally separated by narrowing the emission line widths at low temperature. In the case of the Br-rich CsPb(Br/I) 3 QD sample, the partial halide-segregation-induced heterogeneity of the alloy phase within the ensemble at low temperature leads to blue-shifted radiative recombination channels.

Water-dispersible and stable fluorescent CsPbBr 3 perovskite quantum dots (QDs)-loaded polymeric nanospheres were prepared by an emulsification process. Colloidal CsPbBr 3 QDs that were initially prepared in organic solvents were transferred to an aqueous solution by coating with non-ionic amphiphilic polymers, viz., poly(ethyleneoxide)-poly(propyleneoxide)-poly (ethyleneoxide) triblock-copolymer and polyethylene glycolylated hydrogenated castor oil. The polymer-encapsulated CsPbBr 3 QDs-loaded nanospheres have an average diameter of ∼ 55 nm and they disperse well in aqueous solutions without aggregation or flocculation. The fabricated CsPbBr 3 QDs-loaded nanospheres retain their luminescence properties in pure and salt-containing water, which indicates that the polymeric shell of the QDs-polymer nanospheres effectively blocks the diffusion of water and ions into the nanospheres. The results of this study might open many new possibilities for the fluorescent cesium lead halide QDs in a wide variety of applications; for example, they can serve as fluorescent bio-imaging probes.[a] S.

A supra‐quantum dot (SQD) is a three‐dimensionally assembled QD structure composed of several hundreds to thousands of QDs connected through oriented attachments. Owing to their three‐dimensional interconnected structures and relatively large volumes, impurity atoms are thermodynamically more stable in SQDs than in conventional QDs. Herein, we report the facile in‐situ synthesis of colloidal Ag‐doped CdSe SQDs. Ag dopants were efficiently incorporated into CdSe SQDs through the three‐dimensional interconnection of Ag‐doped primary CdSe QDs, as confirmed by elemental analysis combined with chemical etching. Photoelectron spectroscopic studies revealed that the Ag‐doped CdSe SQDs exhibit n‐type doping behavior, since the valence electrons from the interstitial Ag atoms are directly donated to the lattice.