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Lead-halide perovskites exhibit exceptional photovoltaic performance, characterized by unusually long carrier diffusion lengths and recombination times. Paradoxically, these properties persist even in solution-grown crystals dense with defects that should quench carriers. Moreover, the millisecond-scale carrier lifetimes required for efficient energy harvesting appear at odds with nanosecond-range exciton recombination times reported for the same materials.

In this talk, I will present optical and charge transport measurements revealing that key optoelectronic properties of perovskites arise from charge separation induced by localized flexoelectric polarization at interfaces between domains of spontaneous strain — present even in nominally cubic single crystals. Recombination of charge carriers across these domain walls requires tunneling through a potential barrier, naturally accounting for the exponentially long carrier lifetimes, while the carriers remain free to diffuse along domain boundaries over macroscopic distances.

This mechanism provides a natural microscopic link between lattice microstructure and charge transport, resolving longstanding contradictions and offering new design principles for perovskite-based solar cells.