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Revealing Weak Dimensional Confinement Effects in Excitonic Silver/Bismuth Double Perovskites

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journal contribution
posted on 17.12.2021, 14:35 by Martina Pantaler, Valentin Diez-Cabanes, Valentin I. E. Queloz, Albertus Sutanto, Pascal Alexander Schouwink, Mariachiara Pastore, Inés García-Benito, Mohammad Khaja Nazeeruddin, David Beljonne, Doru C. Lupascu, Claudio Quarti, Giulia Grancini
Lead-free perovskites are attracting increasing interest as nontoxic materials for advanced optoelectronic applications. Here, we report on a family of silver/bismuth bromide double perovskites with lower dimensionality obtained by incorporating phenethylammonium (PEA) as an organic spacer, leading to the realization of two-dimensional double perovskites in the form of (PEA)4AgBiBr8 (n = 1) and the first reported (PEA)2CsAgBiBr7 (n = 2). In contrast to the situation prevailing in lead halide perovskites, we find a rather weak influence of electronic and dielectric confinement on the photophysics of the lead-free double perovskites, with both the 3D Cs2AgBiBr6 and the 2D n = 1 and n = 2 materials being dominated by strong excitonic effects. The large measured Stokes shift is explained by the inherent soft character of the double-perovskite lattices, rather than by the often-invoked band to band indirect recombination. We discuss the implications of these results for the use of double perovskites in light-emitting applications.