TY - JOUR
T1 - Direct Observation of Photoexcited Electron Dynamics in Organic Solids Exhibiting Thermally Activated Delayed Fluorescence via Time-Resolved Photoelectron Emission Microscopy
AU - Fukami, Yusuke
AU - Iwasawa, Masato
AU - Sasaki, Masahiro
AU - Hosokai, Takuya
AU - Nakanotani, Hajime
AU - Adachi, Chihaya
AU - Fukumoto, Keiki
AU - Yamada, Yoichi
N1 - Funding Information:
This work was supported financially by MEXT Q‐LEAP lasers for next frontiers in science and technology (ATTO), JSPS KAKENHI Grant No. 20H02808, 19K05182, 18H03902, 15K17677, 17H06141, 21H02015. A part of this work was conducted at the AIST Nano‐Processing Facility supported by “Nanotechnology Platform Program” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. Grant Number JPMXP09A20AT0015.
Funding Information:
This work was supported financially by MEXT Q-LEAP lasers for next frontiers in science and technology (ATTO), JSPS KAKENHI Grant No. 20H02808, 19K05182, 18H03902, 15K17677, 17H06141, 21H02015. A part of this work was conducted at the AIST Nano-Processing Facility supported by “Nanotechnology Platform Program” of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. Grant Number JPMXP09A20AT0015.
Publisher Copyright:
© 2021 Wiley-VCH GmbH
PY - 2021/10/4
Y1 - 2021/10/4
N2 - Solid-state films exhibiting thermally activated delayed fluorescence (TADF) can offer high internal electroluminescence (EL) quantum efficiency, even in a simplified device structure. However, the exciton dynamics in solid-state TADF films, particularly for the unexpected exciton loss processes such as concentration quenching, have not yet been clarified. The dynamics of photoexcited electrons in the TADF process of a 2,4,5,6-Tetra (9H-carbazol-9-yl) isophthalonitrile (4CzIPN) solid film are observed via time-resolved photoelectron emission microscopy (TR-PEEM) and the results are compared with the conventional time-resolved photoluminescence (TR-PL) technique. The initial decay process of the photoexcited electrons probed via TR-PEEM is thoroughly traced in the TR-PL signal, while unusual long-lived electrons are detected only through the use of TR-PEEM. These results indicate that the excitons of 4CzIPN spontaneously dissociate into free carriers within the exciton lifetime, which seems to be a common process that contributes to the exciton loss in polar organic solids.
AB - Solid-state films exhibiting thermally activated delayed fluorescence (TADF) can offer high internal electroluminescence (EL) quantum efficiency, even in a simplified device structure. However, the exciton dynamics in solid-state TADF films, particularly for the unexpected exciton loss processes such as concentration quenching, have not yet been clarified. The dynamics of photoexcited electrons in the TADF process of a 2,4,5,6-Tetra (9H-carbazol-9-yl) isophthalonitrile (4CzIPN) solid film are observed via time-resolved photoelectron emission microscopy (TR-PEEM) and the results are compared with the conventional time-resolved photoluminescence (TR-PL) technique. The initial decay process of the photoexcited electrons probed via TR-PEEM is thoroughly traced in the TR-PL signal, while unusual long-lived electrons are detected only through the use of TR-PEEM. These results indicate that the excitons of 4CzIPN spontaneously dissociate into free carriers within the exciton lifetime, which seems to be a common process that contributes to the exciton loss in polar organic solids.
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U2 - 10.1002/adom.202100619
DO - 10.1002/adom.202100619
M3 - Article
AN - SCOPUS:85108431513
SN - 2195-1071
VL - 9
JO - Advanced Optical Materials
JF - Advanced Optical Materials
IS - 19
M1 - 2100619
ER -