TY - JOUR
T1 - Visualization of Frontier Molecular Orbital Separation of a Single Thermally Activated Delayed Fluorescence Emitter by STM
AU - Zoh, Inhae
AU - Imai-Imada, Miyabi
AU - Bae, Jaehyun
AU - Imada, Hiroshi
AU - Tsuchiya, Youichi
AU - Adachi, Chihaya
AU - Kim, Yousoo
N1 - Funding Information:
The authors gratefully acknowledge Xian-Kai Chen and Jean-Luc Brédas for theoretical calculations and fruitful discussions, as well as Emiko Kazuma, Yoshiko Shimizu, and Yuki Hasegawa for supporting the preparation of the Ag tip. This work was supported in part by JSPS KAKENHI (Grant Nos. 21H04644 and 18H05257). I.Z. was supported by the RIKEN International Program Associate.
Publisher Copyright:
© 2021 American Chemical Society. All rights reserved.
PY - 2021
Y1 - 2021
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.jpclett.1c02140
DO - 10.1021/acs.jpclett.1c02140
M3 - Article
C2 - 34342465
AN - SCOPUS:85113401344
SN - 1948-7185
VL - 12
SP - 7512
EP - 7518
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
ER -