Perspective on High-Resolution Characterizations of Polarons in Halide Perovskites

Polarons play an important role in properties such as charge transport and phase segregation in halide perovskite optoelectronics. Extensive spectroscopic investigations have been performed on polarons in halide perovskites, revealing their spectral and temporal characteristics in the photocarrier and lattice regimes. In this Perspective, we review the capabilities of the respective spectroscopic techniques and the key properties of polarons that have been experimentally observed in the framework of the Fröhlich polaron model. We analyze how transmission electron microscopy (TEM) and related high-resolution characterization techniques can further our understanding of polarons in halide perovskites. For characterization of halide perovskites with TEM, one of the main challenges is the materials' sensitivity to electron beam. We will give an overview of current strategies to mitigate the challenge. We discuss potential research directions, open questions, and remaining challenges that may open the door for polaron engineering in halide perovskite optoelectronics.