Leveraging Low-Energy Structural Thermodynamics in Halide Perovskites

Metal halide perovskites
(MHPs) combine extraordinary optoelectronic
properties with chemical and mechanical properties not found in their
semiconductor counterparts. For instance, they exhibit optoelectronic
properties on par with single-crystalline gallium arsenide yet exhibit
near-zero formation energies. The small lattice energy of MHPs means
they undergo a rich diversity of polymorphism near standard conditions
like organic materials. MHPs also demonstrate ionic transport as high
as state-of-the-art battery electrodes. The most widespread applications
for metal halide perovskites (e.g., photovoltaics and solid-state
lighting) typically view low formation energies, polymorphism, and
high ion transport as a nuisance that should be eliminated. Here,
we put these properties into perspective by comparing them to other
technologically relevant semiconductors to highlight how unique this
combination of properties are for semiconductors and to illustrate
ways to leverage these properties in emerging applications.