UC San Diego

Halide perovskites exhibit complex behaviors across multiple length and time scales, ranging from dipole coupling that gives rise to cooperative emission to nanoscale lattice distortions that govern their optoelectronic response. Many of these phenomena emerge on ultrafast timescales or at nanoscale dimensions, making them difficult to resolve using conventional characterization techniques.In this dissertation, advanced optical and structural probes are developed to uncover these hidden phenomena in halide perovskites. First, in epitaxial perovskite superlattices, the formation and dynamics of a collective excited state associated with super fluorescence are revealed, providing insight into how microscopic dipoles synchronize to generate macroscopic coherent emission. Second, nanoscale strain, lattice distortion, and crystal rotation are precisely mapped in high-performance perovskite solar cells. These measurements uncover pronounced structural heterogeneity and guide a steric strategy that homogenizes local strain, leading to improved photovoltaic performance and stability.Together, these studies demonstrate how advanced optical and structural probes can bridge microscopic phenomena and macroscopic functionalities in halide perovskites.