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Two-dimensional optical excitations in mixed-valence Cs2Au2I6 fully inorganic double perovskite

Abstract

In the continuous quest for more performing materials in photovoltaics, we have here investigated the electronic and optical properties of the mixed-valence Cs2Au2I6 fully inorganic double perovskite. In particular, moving from previous experimental and theoretical analyses we have calculated, by means of a combined fully ab-initio approach based on density functional and many-body perturbation theory, the quasi-particle and excitonic features of such very appealing and overlooked material. The interest is indeed associated with a charge transfer from the valence band to an intermediate band that are both constituted by the same atom (Au) but in a different oxidation state, i.e. +1 in the valence band and +3 in the intermediate band. The electronic band gap calculated within the GW method is direct and is 1.35 eV, a value of extreme interest for any possible solar-harvesting application. Moreover the importance of including both local field effects and electron-hole interaction in the calculation of the optical properties of the material is clearly demonstrated by solving the Bethe-Salpeter Equation. The quasi-2D exciton spatial localization is revealed, feature that well correlates with the in-plane Au(I)→Au(III) charge transfer.

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Publication details

The article was received on 15 Jul 2018, accepted on 11 Sep 2018 and first published on 13 Sep 2018


Article type: Communication
DOI: 10.1039/C8TC03496F
Citation: J. Mater. Chem. C, 2018, Accepted Manuscript
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    Two-dimensional optical excitations in mixed-valence Cs2Au2I6 fully inorganic double perovskite

    G. Giorgi, K. Yamashita and M. Palummo, J. Mater. Chem. C, 2018, Accepted Manuscript , DOI: 10.1039/C8TC03496F

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