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Published on: May 29, 2018
Variation of the optical properties with size and composition of small, isolated Cdx Sey + clusters
1Technische Universität Darmstadt, Eduard-Zintl Institut für Anorganische und Physikalische Chemie, Darmstadt, Germany.
Abstract:
Global energy minimum structures and optoelectronic properties are presented for isolated Cdx Sey + clusters with x + y ≤ 26. The compositional- and size-dependent variation of optical, electronic and geometric properties is systematically studied within the framework of ground state and time-dependent density functional theory. The applied methods are justified by benchmarks with experimental data. It is shown that the optical gap can be tuned by more than 2 eV by only changing the composition for a fixed number of atoms. The stoichiometric species reveal an unexpected size-dependent behavior in comparison to larger colloidal CdSe quantum dots, that is, a redshift of the optical gap was observed with decreasing cluster size in contrast to predictions by quantum-size effects. This unexpected result is discussed in detail taking the positive charge of the clusters into account.
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