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Highly Absorbing Lead-Free Semiconductor Cu₂AgBiI₆ for Photovoltaic Applications from the Quaternary CuI-AgI-BiI₃ Phase Space

Sansom, HC; Longo, G; Wright, AD; Buizza, LRV; Mahesh, S; Wenger, B; Zanella, M; ... Rosseinsky, MJ; + view all (2021) Highly Absorbing Lead-Free Semiconductor Cu₂AgBiI₆ for Photovoltaic Applications from the Quaternary CuI-AgI-BiI₃ Phase Space. Journal of the American Chemical Society 10.1021/jacs.1c00495. (In press). Green open access

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Abstract

Since the emergence of lead halide perovskites for photovoltaic research, there has been mounting effort in the search for alternative compounds with improved or complementary physical, chemical, or optoelectronic properties. Here, we report the discovery of Cu_{2}AgBiI_{6}: a stable, inorganic, lead-free wide-band-gap semiconductor, well suited for use in lead-free tandem photovoltaics. We measure a very high absorption coefficient of 1.0 × 10^{5} cm^{–1} near the absorption onset, several times that of CH_{3}NH_{3}PbI_{3}. Solution-processed Cu2AgBiI6 thin films show a direct band gap of 2.06(1) eV, an exciton binding energy of 25 meV, a substantial charge-carrier mobility (1.7 cm^{2} V^{–1} s^{–1}), a long photoluminescence lifetime (33 ns), and a relatively small Stokes shift between absorption and emission. Crucially, we solve the structure of the first quaternary compound in the phase space among CuI, AgI and BiI_{3}. The structure includes both tetrahedral and octahedral species which are open to compositional tuning and chemical substitution to further enhance properties. Since the proposed double-perovskite Cs2AgBiI6 thin films have not been synthesized to date, Cu_{2}AgBiI_{6} is a valuable example of a stable Ag^{+}/Bi^{3+} octahedral motif in a close-packed iodide sublattice that is accessed via the enhanced chemical diversity of the quaternary phase space.

Type: Article
Title: Highly Absorbing Lead-Free Semiconductor Cu₂AgBiI₆ for Photovoltaic Applications from the Quaternary CuI-AgI-BiI₃ Phase Space
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/jacs.1c00495
Publisher version: https://doi.org/10.1021/jacs.1c00495
Language: English
Additional information: © 2021 The Authors. Published by American Chemical Society. This is an Open Access article published under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > MAPS Faculty Office
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > MAPS Faculty Office > Institute for Materials Discovery
URI: https://discovery.ucl.ac.uk/id/eprint/10123911
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