Perylene diimide (PDI) molecules possess high optical absorption and fluorescence yield, and great photochemical stability.Their strong electron-accepting properties have led to the development of a class of non-fullerene acceptors (NFAs) for organic solar cell applications. PDI-based NFA structures are typically designed to prevent strong π-π aggregation, because excitations are often trapped in geometries where PDIs are tightly associated. Characterization of the intermolecular geometry between PDI molecules in thin films is therefore crucial for developing better PDI-based NFAs, which are typically blended with a donor molecule or polymer in bulk heterojunction active layers. Using infrared reflectance-absorbance spectroscopy (IRRAS), we seek to establish spectral-structure relationships for different PDI intermolecular geometries, in order to enable future characterization of PDI packing in bulk heterojunctions. By varying the incidence angle and polarization of the IR beam, a series of PDI derivatives with different crystal packing were studied. Here, we report changes in relative peak intensity and shifts in frequency for the IRRA spectra as a function of different crystal packing geometries, and connect this to changes in specific non-covalent interactions in the thin films.

Mapping spectral-structure relationships of crystal packing in PDI thin films using infrared reflectance absorbance spectroscopy

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.