Visualization of Frontier Molecular Orbital Separation of a Single Thermally Activated Delayed Fluorescence Emitter by STM

Inhae Zoh, Miyabi Imai-Imada, Jaehyun Bae, Hiroshi Imada, Youichi Tsuchiya, Chihaya Adachi, Yousoo Kim

Research output: Contribution to journalArticlepeer-review

Abstract

Because the spatial distribution of frontier molecular orbitals (FMOs) regulates the thermally activated delayed fluorescence (TADF) property, researchers synthesize TADF emitters by designing their FMO distribution. However, it remains challenging to clarify how the FMO distribution is altered at molecular interfaces. Thus, visualizing the FMOs at molecular interfaces helps us to understand the working behavior of TADF emitters. Using scanning tunneling microscopy (STM), we investigated the electronic structure of a single TADF emitter, hexamethylazatriangulene-triazine, at molecule-metal and molecule-insulating film interfaces. FMOs at the molecule-metal interface were not spatially confined to the donor-acceptor moieties because of hybridization. Meanwhile, FMOs at the molecule-insulator interface exhibited spatially separated filled and empty states confined to each moiety, similar to the calculated gas-phase FMOs. These observations illustrate that the molecule-environment interaction alters the spatial distribution of FMOs, proving that STM is a powerful tool for studying TADF molecules.

Original languageEnglish
Pages (from-to)7512-7518
Number of pages7
JournalJournal of Physical Chemistry Letters
Volume12
DOIs
Publication statusPublished - 2021

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Physical and Theoretical Chemistry

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