Electrostatic potential imaging of phase-separated structures in organic materials via differential phase contrast scanning transmission electron microscopy

Shin Inamoto; Satoru Shimomura; Yuji Otsuka

doi:10.1093/jmicro/dfaa027

Electrostatic potential imaging of phase-separated structures in organic materials via differential phase contrast scanning transmission electron microscopy

Microscopy (Oxf). 2020 Oct 30;69(5):304-311. doi: 10.1093/jmicro/dfaa027.

Authors

Shin Inamoto¹, Satoru Shimomura², Yuji Otsuka¹

Affiliations

¹ Morphological Research Laboratory, Toray Research Center, Inc., 3-7, Sonoyama 3-chome, Otsu, Shiga 520-8567, Japan.
² Advanced Materials Research Laboratories, Toray Industries, Inc., 2-1, Sonoyama 3-chome, Otsu, Shiga 520-0842, Japan.

PMID: 32453389
DOI: 10.1093/jmicro/dfaa027

Abstract

Electron staining is generally performed prior to observing organic materials via transmission electron microscopy (TEM) to enhance image contrast. However, electron staining can deteriorate organic materials. Here, we demonstrate electrostatic potential imaging of organic materials via differential phase contrast (DPC) scanning transmission electron microscopy (STEM) without electron staining. Electrostatic potential imaging drastically increases the contrast between different materials. Phase-separated structures in a poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend that are impossible to observe using conventional STEM are clearly visualized. Furthermore, annealing behavior of the phase-separated structures is directly observed. The morphological transformations in the samples are consistent with their physical parameters, including their glass transition and melting temperatures. Our results indicate that electrostatic potential imaging is highly effective for observing organic materials.

Keywords: differential phase contrast; organic materials; organic photovoltaic; phase-separated structure; scanning transmission electron microscopy.