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Title: Synthesis and Optical Properties of Colloidal M3Bi2I9 (M = Cs, Rb) Perovskite Nanocrystals
Authors: PAL, JAYA
Chakraborty, Sudip
Das, Shyamashis
Dept. of Chemistry
Dept. of Physics
Keywords: Zero-dimensional
Crystal structure
Metal halide
Perovskite nanocrystals
Issue Date: Apr-2018
Publisher: American Chemical Society
Citation: Journal of Physical Chemistry C, 122(19), 10643-10649.
Abstract: Bulk Cs3Bi2I9 exhibits zero-dimensional (0-D) perovskite crystal structure at the molecular level, providing scopes for novel optical properties compared to three-dimensional perovskite structures. Here, 0-D refers to the crystal structure irrespective of the size of the crystal. We have prepared colloidal Cs3Bi2I9 nanocrystals and elucidated the unique optical properties arising from their 0-D crystal structure. Absorption spectrum at 10 K confirms that the electronic band gap of Cs3Bi2I9nanocrystals is at 2.86 eV, along with a sharp excitonic peak at 2.56 eV, resulting in a very high excitonic binding energy, EbX = 300 meV. Interestingly, we observe two peaks in the photoluminescence spectra at room temperature on both sides of the excitonic absorption energy. Because EbX (300 meV) ? effective phonon energy (36 meV), the phonon-mediated relaxation of carriers from conduction band minimum to the excitonic state is suppressed to an extent. Consequently, two photoluminescence peaks related to both the bulk band edge and the excitonic transitions are observed. Furthermore, Rb3Bi2I9 nanocrystals have also been synthesized, but they exhibit two-dimensional layered structure, unlike the 0-D structure of Cs3Bi2I9.
ISSN: 1932-7447
Appears in Collections:JOURNAL ARTICLES

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