The APbX3 perovskites (A = monovalent cation, X = halide) exhibit remarkable properties as solar-cell absorbers, including direct bandgaps suitable for visible-light absorption, long carrier recombination lifetime, and inexpensive film deposition methods. However, these materials have intrinsic instabilities and even the origin of the materials' superior photophysical properties are still under debate. Finding both structural and functional analogs of a material is a time-tested approach for understanding which design principals must be reproduced in an analog. I will discuss our attempts at capturing the optical properties of APbX3 perovskites in both lower-dimensional analogs as well as in lead-free materials. The ABX3 perovskites constrain the B-site metals to divalent cations, limiting the number of analogs we can synthesize. We recently showed that the family of A2BB'X6 double perovskites, which can accommodate a much greater range of B-site metals, has promising optical properties as absorbers. Armed with this substitutional flexibility, we have explored alternative metals that can be incorporated into the perovskite lattice. Studying the electronic differences between the lead perovskites and lead-free double perovskites has allowed us to tune double perovskites to better absorb sunlight. I will share our understanding of these materials, including the basis for the dramatic effects of dilute impurity alloying of double perovskites.

Capturing the properties of lead-halide perovskites with new materials

255th National Meeting (2018)

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