2, University of California, Berkeley, Berkeley, California, United States
3, Lawrence Berkeley National Laboratory, Berkeley, California, United States
The APbX3 perovskites (A = monovalent cation, X = halide) exhibit remarkable properties as solar-cell absorbers. However, these materials have intrinsic instabilities and even the origin of the materials' superior photophysical properties is still under debate. Finding both structural and functional analogs of a material is important for understanding which design principals must be reproduced in an analog. I will discuss our attempts at capturing the photophysical properties of APbX3 perovskites with new compositions and new inorganic architectures.
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 metals, have 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 have allowed us to understand how to tune double perovskites to better absorb sunlight. I will share our understanding of these materials, including the basis for dramatic reduction in bandgaps induced through dilute impurity alloying. I will also present new materials developed in my group as light absorbers, which deviate from the typical perovskite lattice.