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Issue 6, 2017
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Colloidal thallium halide nanocrystals with reasonable luminescence, carrier mobility and diffusion length

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Abstract

Colloidal lead halide based perovskite nanocrystals (NCs) have been recently established as an interesting class of defect-tolerant NCs with potential for superior optoelectronic applications. The electronic band structure of thallium halides (TlX, where X = Br and I) show a strong resemblance to lead halide perovskites, where both Pb2+ and Tl+ exhibit a 6s2 inert pair of electrons and strong spin–orbit coupling. Although the crystal structure of TlX is not perovskite, the similarities of its electronic structure with lead halide perovskites motivated us to prepare colloidal TlX NCs. These TlX NCs exhibit a wide bandgap (>2.5 eV or <500 nm) and the potential to exhibit a reduced density of deep defect states. Optical pump terahertz (THz) probe spectroscopy with excitation fluence in the range of 0.85–5.86 × 1013 photons per cm2 on NC films shows that the TlBr NCs possess high effective carrier mobility (∼220 to 329 cm2 V−1 s−1), long diffusion length (∼0.77 to 0.98 μm), and reasonably high photoluminescence efficiency (∼10%). This combination of properties is remarkable compared to other wide-bandgap (>2.5 eV) semiconductor NCs, which suggests a reduction in the deep-defect states in the TlX NCs. Furthermore, the ultrafast carrier dynamics and temperature-dependent reversible structural phase transition together with its influence on the optical properties of the TlX NCs are studied.

Graphical abstract: Colloidal thallium halide nanocrystals with reasonable luminescence, carrier mobility and diffusion length

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Publication details

The article was received on 17 Mar 2017, accepted on 10 Apr 2017 and first published on 19 Apr 2017


Article type: Edge Article
DOI: 10.1039/C7SC01219E
Citation: Chem. Sci., 2017,8, 4602-4611
  • Open access: Creative Commons BY license
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    Colloidal thallium halide nanocrystals with reasonable luminescence, carrier mobility and diffusion length

    W. J. Mir, A. Warankar, A. Acharya, S. Das, P. Mandal and A. Nag, Chem. Sci., 2017, 8, 4602
    DOI: 10.1039/C7SC01219E

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