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Abstract New light is shed on the previously known perovskite material, Cs2Au2I6, as a potential active material for high‐efficiency thin‐film Pb‐free photovoltaic cells. First‐principles calculations demonstrate that Cs2Au2I6has an optimal band gap that is close to the Shockley–Queisser value. The band gap size is governed by intermediate band formation. Charge disproportionation on Au makes Cs2Au2I6a double‐perovskite material, although it is stoichiometrically a single perovskite. In contrast to most previously discussed double perovskites, Cs2Au2I6has a direct‐band‐gap feature, and optical simulation predicts that a very thin layer of active material is sufficient to achieve a high photoconversion efficiency using a polycrystalline film layer. The already confirmed synthesizability of this material, coupled with the state‐of‐the‐art multiscale simulations connecting from the material to the device, strongly suggests that Cs2Au2I6will serve as the active material in highly efficient, nontoxic, and thin‐film perovskite solar cells in the very near future.
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Is Cs 2 TiBr 6 a promising Pb-free perovskite for solar energy applications?
In a quest for Pb-free perovskites suitable for solar energy applications, Cs 2 TiBr 6 has recently been reported as a promising compound, with appropriate optical and electrical properties as well as high stability under environmental stresses. In this study, we pursue investigation on this compound, demonstrating phase pure Cs 2 TiBr 6 powder formation using solution synthesis and providing complementary experimental characterization and theoretical calculations. An experimental absorption onset of around 2.0 eV is extracted and a weak broad photoluminescence is measured. Density functional theory calculations predict an indirect bandgap, parity-forbidden for both the direct and indirect transitions, which explains the weak and Stokes shifted luminescence. Additionally, we highlight the strong instability of Cs 2 TiBr 6 powder in ambient atmosphere. Therefore, our experimental results supported by theoretical calculations differ from previous results and raise doubts on the suitability of Cs 2 TiBr 6 in its pristine form for solar energy applications.
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- Award ID(s):
- 1709294
- PAR ID:
- 10165957
- Date Published:
- Journal Name:
- Journal of Materials Chemistry A
- Volume:
- 8
- Issue:
- 7
- ISSN:
- 2050-7488
- Page Range / eLocation ID:
- 4049 to 4054
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9ta13870f
