Perylene diimide (PDI) dyes are known for their pronounced crystallochromism, photophysical stability, chemical tunability, and propensity to undergo a photon downconversion process called singlet fission. Our group has recently studied the relation between optical absorption and molecular coupling at the substrate-PDI interface using electronic sum-frequency generation (ESFG). PDI absorption spectra are intimately connected to the underlying PDI crystal structure through interactions between neighboring PDI molecules, which can be described using a tight-binding Holstein-style Hamiltonian. Moreover, the local geometry that dictates a film’s absorption also modulates the film’s singlet fission kinetics and energy transport. The substrate-PDI interface, however, presents a different environment from the bulk film and creates the possibility of inhomogenous transport properties and electronic structure. To efficiently utilize PDIs in hybrid device structures, the hetero-interface must be considered.<br/><br/>In conjunction with bulk analysis, we studied the interfacial density of states and geometry of PDI thin films using polarization resolved broadband ESFG. Our ESFG spectra show an optical band gap narrowing at the interface, which is qualitatively reproduced with our tight-binding model through a small slip-stack change in intermolecular geometry. Moreover, the polarization resolved experiments allow us to map the ESFG response to a net PDI orientation near the PDI-substrate interface that depends on the derivative of PDI used. These findings suggest excitations migrate towards the PDI-substrate interface and demonstrate how ESFG evidences the structure and properties of thin films near important interfaces.

Probing the interfacial electronic density of states of perylene diimide thin films using electronic sum-frequency generation

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

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