Abstract

What is the relation between the structural dynamics of crystals and their functional properties at finite temperatures? Recent studies of halide perovskite semiconductors showed that despite being mechanically soft and having many structural defects, they have excellent optoelectronic properties. We and others have shown that a key fundamental property for their surprising optoelectronic properties is their strongly anharmonic (i.e., nonlinear) lattice dynamics. Inspired by these findings, we turned to investigate anharmonic effects in the lattice dynamics of organic semiconducting crystals that are even softer, mechanically, than the halide perovskites. I will present Raman scattering studies that show a plethora of expressions of anharmonicity in the structural dynamics of organic crystals. Then, I will discuss how the character of the structural dynamics can be tuned by introduction of molecular sidechains. Finally, I will discuss implications of the anharmonic lattice dynamics on the electronic properties of these crystals.