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

Sansom, Harry, Longo, Giulia, Wright, Adam, Buizza, Leonardo, Mahesh, Suhas, Wenger, Bernard, Zanella, Marco, Abdi-Jalebi, Mojtaba, Pitcher, Michael, Dyer, Matthew, Manning, Troy, Friend, Richard, Herz, Laura, Snaith, Henry, Claridge, John and Rosseinsky, Matthew (2020) Highly Absorbing Lead-Free Semiconductor Cu2AgBiI6 for Photovoltaic Applications from the Quaternary CuI-AgI-BiI3 Phase Space. [Data Collection]

Description

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 Cu2AgBiI6; 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 × 105 cm-1 near the absorption onset, several times that of CH3NH3PbI3. 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 cm2V-1s-1), long photoluminescence lifetimes (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 between CuI, AgI and BiI3. The structure includes both tetrahedral and octahedral species which are open to compositional tuning and chemical substitution to further enhance properties. As the proposed double perovskite Cs2AgBiI6 thin films have not been synthesized to date, Cu2AgBiI6 is a valuable example of a stable Ag+/Bi3+ octahedral motif in a close-packed iodide sub-lattice that is accessed via the enhanced chemical diversity of the quaternary phase space.

Keywords: lead-free photoabsorbers, crystal structure, Cu-Ag-Bi-I, 3D BiI network
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Troy Manning
Date Deposited: 10 Mar 2021 13:05
Last Modified: 10 Mar 2021 13:05
DOI: 10.17638/datacat.liverpool.ac.uk/1110
URI: https://datacat.liverpool.ac.uk/id/eprint/1110

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