Mapping the Diffusion Tensor in Microstructured Perovskites

TL;DR

This paper introduces a diffusion tensor framework to analyze energy transport in heterogeneous perovskite materials, revealing anisotropic diffusion properties and grain boundary effects through high-resolution photoluminescence data.

Contribution

The study develops a novel diffusion tensor-based model for analyzing anisotropic energy transport in microstructured semiconductors, integrating spatial and temporal PL data.

Findings

29% difference in diffusion coefficients between grains

Alignment of diffusion tensors in electronically coupled grains

Framework enables detailed understanding of energy transport in heterogenous materials

Abstract

Understanding energy transport in semiconductors is critical for design of electronic and optoelectronic devices. Semiconductor material properties such as charge carrier mobility or diffusion length are commonly measured in bulk crystals and determined using models that describe transport behavior in homogeneous media, where structural boundary effects are minimal. However, most emerging semiconductors exhibit nano and microscale heterogeneity. Therefore, experimental techniques with high spatial resolution paired with models that capture anisotropy and domain boundary behavior are needed. We develop a diffusion tensor-based framework to analyze experimental photoluminescence (PL) diffusion maps accounting for material nano and microstructure. Specifically, we quantify both carrier transport and recombination in single crystal and polycrystalline lead halide perovskites by globally fitting diffusion maps, with spatial, temporal, and PL intensity data. We reveal a 29% difference in principal diffusion coefficients and alignment between electronically coupled grains for CH3NH3PbI3 polycrystalline films. This framework allows for understanding and optimizing anisotropic energy transport in heterogeneous materials.