Exciton Relaxation Dynamics in Perovskite Cs₄PbBr₆ Nanocrystals

Abstract

Lower-dimensional metal halide perovskites have been recognized as an efficient white light emitter. The broad band emission spectrum originates from the recombination of excited charge carriers through free excitons (FEs), self-trapped excitons (STEs), and defect-trapped excitons. However, the emission properties of zero-dimensional (0-D) perovskites have not been explored extensively. Here, in this work, we have performed low-temperature absorbance, photoluminescence (PL), PL excitation (PLE), PL lifetime, and Raman measurements to understand the exciton relaxation processes in Cs 4 PbBr 6 NCs. Our experimental observations indicate that two distinct UV light spectra evolved from the photoexcited carrier recombination through FE and STE states. We emphasize that such UV light sources can be beneficial for various applications, like curing of materials, disinfection of viruses, hygiene control, etc.

Fast Intrinsic Emission Quenching in Cs4PbBr6 Nanocrystals

“…Consequently, the bandgap of the bulk 0D at room temperature of 3.95 eV is quasi-identical to that of a hypothetical isolated Cs 4 PbBr 6 molecule . The formation of small and highly energetic polarons and self-trapped excitons − enabled by such strong electronic localization makes 0D halides appealing from both fundamental and applicative standpoints.…”

Free and self-trapped exciton emission in perovskite CsPbBr3 microcrystals

“…[40][41][42][43][44][45][46][47][48] Since the lattice deformation in these structures is easy to occur. In the fully inorganic Cs-Pb-Br systems, the STE emission was mainly discussed in zero-dimensional Cs 4 PbBr 6 , [49][50][51] in which the [PbBr 6 ] À octahedrons are isolated. An STE band was also detected from the low energy wing of the PL spectra of CsPbBr 3 and CsPb(Br 1Àx I x ) 3 quantum dots under weak excitation condition, 52 but this conclusion has not been widely accepted.…”

Highly stable and water dispersible polymer-coated CsPbBr3 nanocrystals for Cu-ion detection in water

“…10,62 The additional XRD diffraction peaks located at 2θ values of 12.91°, 20.34°, 22.66°, 25.68°, 27.77°, 28.84°, 30.55°, 34.18°, 39.26°, and 46.07° are signifying the (110), ( 113), (300), ( 024), ( 131), ( 214), ( 223), ( 134), (324), and (600) lattice planes of the rhombohedral Cs4PbBr6 crystal structure (PDF #01-73-2478). 50,63 The contribution of rhombohedral Cs4PbBr6 phases is quite high as compared to monoclinic CsPbBr3 phases. The XRD diffraction pattern of PbN-1 NCs reveals three perovskite phases, i.e., 3D CsPbBr3 (monoclinic phase), 0D Cs4PbBr6 (rhombohedral phase), and 2D CsPb2Br5 (tetragonal phase) crystal structures.…”