Imaging material functionality through 3D nanoscale tracking of energy flow

TL;DR

This paper introduces a non-invasive optical method to track energy carriers in materials at nanoscale and ultrafast timescales, revealing how disorder and morphology influence energy flow in semiconductors.

Contribution

It presents a novel interferometric scattering technique for 4D mapping of energy transport in materials, enabling direct correlation with morphology and disorder effects.

Findings

Visualized exciton, charge, and heat transport in various semiconductors.

Showed morphological boundaries affect energy flow and resistivity.

Provided insights for designing defect-tolerant semiconductor materials.

Abstract

The ability of energy carriers to move between atoms and molecules underlies biochemical and material function. Understanding and controlling energy flow, however, requires observing it on ultrasmall and ultrafast spatiotemporal scales, where energetic and structural roadblocks dictate the fate of energy carriers. Here we developed a non-invasive optical scheme that leverages non-resonant interferometric scattering to track tiny changes in material polarizability created by energy carriers. We thus map evolving energy carrier distributions in four dimensions of spacetime with few-nanometer lateral precision and directly correlate to material morphology. We visualize exciton, charge, and heat transport in polyacene, silicon and perovskite semiconductors and elucidate how disorder affects energy flow in 3D. For example, we show that morphological boundaries in polycrystalline metal halide perovskites possess lateral- and depth-dependent resistivities, blocking lateral transport for surface but not bulk carriers. We furthermore reveal strategies to interpret energy transport in disordered environments that will direct the design of defect-tolerant materials for the semiconductor industry of tomorrow.