I will discuss the consequences of dimensional confinement on halide double perovskites uncovered by synthesizing lower-dimensional analogues of three-dimensional double perovskites. For example, the layered perovskites (BA)4AgBiBr8 and (BA)2CsAgBiBr7 (BA = CH3(CH2)3NH3+) feature metal-halide sheets of mono and bilayer thickness, respectively, where the ordered three-dimensional double-perovskite lattice of Cs2AgBiBr6 is partitioned by organic cations. While the effects of dimensional confinement have long been studied in lead-based halide perovskites, this series of materials represents the first opportunity to explore dimensional reduction in halide double perovskites. Notably, electronic structure calculations indicate that the indirect bandgap of Cs2AgBiBr6 becomes direct when the infinitely thick inorganic lattice is reduced to monolayer thickness. Calculations on model systems allow us to separate the effects of dimensional reduction from those of the accompanying structural distortions in the inorganic sublattice. Detailed optical characterization shows that the photophysical properties of our layered double perovskites are markedly different than those of their well-studied lead-halide analogs. Hybrid layered derivatives of double perovskites substantially expand on the substitutional flexibility of halide perovskites to encompass greater compositional and electronic diversity.

Dimensional reduction of halide double perovskites

2019 Fall National Meeting

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