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Published January 10, 2020 | Supplemental Material
Journal Article Open

Size-Dependent Lattice Structure and Confinement Properties in CsPbI₃ Perovskite Nanocrystals: Negative Surface Energy for Stabilization


CsPbI₃ nanocrystals with narrow size distributions were prepared to study the size-dependent properties. The nanocrystals adopt the perovskite (over the nonperovskite orthorhombic) structure with improved stability over thin-film materials. Among the perovskite phases (cubic α, tetragonal β, and orthorhombic γ), the samples are characterized by the γ phase, rather than α, but may have a size-dependent average tilting between adjacent octahedra. Size-dependent lattice constants systematically vary 3% across the size range, with unit cell volume increasing linearly with the inverse of size to 2.1% for the smallest size. We estimate the surface energy to be from −3.0 to −5.1 eV nm⁻² for ligated CsPbI₃ nanocrystals. Moreover, the size-dependent bandgap is best described using a nonparabolic intermediate confinement model. We experimentally determine the bulk bandgap, effective mass, and exciton binding energy, concluding with variations from the bulk α-phase values. This provides a robust route to understanding γ-phase properties of CsPbI₃.

Additional Information

© 2019 American Chemical Society. Received: November 3, 2019; Accepted: December 18, 2019; Published: December 18, 2019. This work (NC synthesis, size-dependent analysis) was supported by the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center funded by the Office of Science, Office of Basic Energy Sciences within the U.S. Department of Energy. This work was authored in part by the Alliance for Sustainable Energy, Limited Liability Company, the manager and operator of the National Renewable Energy Laboratory under Contract No. DE-AC36-08GO28308. The views expressed in the article do not necessarily represent the views of the Department of Energy or the U.S. Government. Q.Z. acknowledges fellowship support from the China Scholarship Council, Natural Science Foundation of Tianjin (18JCZDJC31000), and Natural Science of Foundation China (21576140). L.T.S. was supported by the U.S. Department of Energy (DOE) Solar Energy Technology Office (SETO) of the Energy Efficiency and Renewable Energy (EERE) award for the Derisking Halide Perovskite Solar Cells project. The authors thank Matthew C. Beard, Ashley R. Marshall, Jeffrey A. Christians, and Erin M. Sanehira for helpful discussion. The authors declare no competing financial interest.

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October 19, 2023