Soft lattice elasto-plasticity of halide perovskites: origin of multifunctionalities

As archetypal soft lattice materials, halide perovskites exhibit distinctive ‘soft lattice’ features such as ionically mediated deformation, liquid-like polaronic behavior, strong electron–phonon coupling, and anharmonic lattice vibrations, etc., collectively indicating a coexistence of mechanical plasticity (static strain) and elasticity (dynamic mechanical responses). However, a unified understanding of these behaviors and their implications for structure–function relationships remain insufficiently developed, particularly from a mechanics-informed perspective. This review reframes halide perovskites through the dual lens of spatial (static strain and plastic deformation) and temporal (dynamic strain and elastic response) mechanics. We systematically dissect the origins, manifestations, and effects of strain in halide perovskites across multiple scales, beginning with the fundamental mechanics and strain-property correlations. The review then differentiates static (plastic) and dynamic (elastic) strain regimes, examining their structural origins, measurable signatures, and implications for synthesis, performance, and stability—culminating in a forward-looking discussion of key challenges and emerging opportunities. By positioning strain as a generative and tunable dimension of material behavior, this work offers new insights into the design of adaptive, mechanically responsive optoelectronic material systems.