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Abstract All‐inorganic lead halide perovskite nanocrystals (NCs) have great optoelectronic properties with promising applications in light‐emitting diodes (LEDs), lasers, photodetectors, solar cells, and photocatalysis. However, the intrinsic toxicity of Pb and instability of the NCs impede their broad applications. Shell‐coating is an effective method for enhanced environmental stability while reducing toxicity by choosing non‐toxic shell materials such as metal oxides, polymers, silica, etc. However, multiple perovskite NCs can be encapsulated within the shell material and a uniform epitaxial‐type shell growth of well‐isolated NCs is still challenging. In this work, lead‐free vacancy‐ordered double perovskite Cs2SnX6(X = Cl, Br, and I) shells are epitaxially grown on the surface of CsPbX3NCs by a hot‐injection method. The effectiveness of the non‐toxic double perovskite shell protection is demonstrated by the enhanced environmental and phase stability against UV illumination and water. In addition, the photoluminescence quantum yields (PL QYs) increase for the CsPbCl3and CsPbBr3NCs after shelling because of the type I band alignment of the core/shell materials, while enhanced charge transport properties obtained from CsPbI3/Cs2SnI6core/shell NCs are due to the efficient charge separation in the type II core/shell band alignment.
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Mixed Valence Perovskite Cs 2 Au 2 I 6 : A Potential Material for Thin‐Film Pb‐Free Photovoltaic Cells with Ultrahigh Efficiency
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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- Award ID(s):
- 1719353
- PAR ID:
- 10051111
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 30
- Issue:
- 12
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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