Revealing Weak Dimensional Confinement Effects in Excitonic Silver/Bismuth Double Perovskites
Martina Pantaler, Valentín Diez‐Cabanes, Valentin I. E. Queloz, Albertus Adrian Sutanto, Pascal Schouwink, Mariachiara Pastore, Inés García‐Benito, Mohammad Khaja Nazeeruddin, David Beljonne, Doru C. Lupascu, Claudio Quarti, Giulia Grancini
Abstract
High Resolution Image Download MS PowerPoint Slide 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) 4 AgBiBr 8 ( n = 1) and the first reported (PEA) 2 CsAgBiBr 7 ( 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 Cs 2 AgBiBr 6 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.