| Abstract Scope |
Lead halide perovskites (LHPs) have emerged as a promising class of solution processable semiconductors, showing outstanding performance in optoelectronic applications including photovoltaics, solid-state lighting, and photodetection. Many of these properties originate from their soft anharmonic lattice dynamics, a unique feature among crystalline semiconductors. In this talk, I will discuss recent advances in understanding phonon anharmonicity of halide perovskites and explore its implications on the functional behaviors of these materials. On the optoelectronic side, we show large amplitude, highly anharmonic lattice displacements produce local polar fluctuations, dynamically stabilizing band edge charge carriers inside a crystalline lattice akin to solvation of excited fluorophore in polar liquids. We further examine the generality of this dynamic carrier relaxation behavior by tuning the halide mass. On the structural side, we show that soft bonding leads to easy formation and coherent switching of ferroelastic twin domains across the LHP family. The twin domain walls produce finite internal reflections and optically steer photon recycling. We suggest LHP twin domain walls be used as optical guides of internal energy transport, introducing a novel device component with non-volatile on-off switching and tunable positioning, enabled by their soft anharmonic lattice. |