TY - JOUR
T1 - Effect of Vibronic Coupling on Correlated Triplet Pair Formation in the Singlet Fission Process of Linked Tetracene Dimers
AU - Shizu, Katsuyuki
AU - Adachi, Chihaya
AU - Kaji, Hironori
N1 - Funding Information:
The quantum chemical calculations using the Q-Chem program package were performed using the SuperComputer System, Institute for Chemical Research, Kyoto University. This work was supported by the Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project, under JST ERATO grant number JPMJER1305, Japan. This work was also supported by JSPS KAKENHI grant number: 17H01231, 17K14529, and 19K05629.
Publisher Copyright:
© 2020 American Chemical Society.
PY - 2020/5/7
Y1 - 2020/5/7
N2 - Tetracene-based singlet fission (SF) materials show application prospects as triplet sensitizers in organic optoelectronics. SF involves internal conversion from photoexcited singlet states 1(S1S0) to correlated triplet pair states 1(T1T1). We derive an expression for the internal conversion rate on the basis of the Fermi golden rule with an artificial Lorentzian broadening. The internal conversion rate depends on the interstate vibronic couplings (VCs) and energy difference (ΔESF) between 1(S1S0) and 1(T1T1). Therefore, understanding the interplay between interstate VCs and ΔESF is necessary to reveal how the structure-property relationship affects the SF efficiency. Here, we propose a method to quantitatively analyze interstate VCs between 1(S1S0) and 1(T1T1). We apply this method to SF in ortho-, meta-, and para-bis(ethynyltetracenyl)benzene and identify an effect of interstate VCs on the 1(T1T1) formation rate. The interstate VCs of the meta dimer are remarkably weak, which reasonably explains the experimentally obtained slow 1(T1T1) formation rate. The weak VCs result from a very small overlap density between 1(S1S0) and 1(T1T1) of the meta dimer. Furthermore, we investigate structure-dependence of the 1(T1T1) formation rate of the para dimer and find that the para dimer shows large VCs and small ΔESF when the rotational angle between the two tetracene units is large, which leads to the faster 1(T1T1) formation rate than those of the ortho and meta dimers. The rotation of the tetracene units is the origin of the experimentally observed fast 1(T1T1) formation rate of the para dimer.
AB - Tetracene-based singlet fission (SF) materials show application prospects as triplet sensitizers in organic optoelectronics. SF involves internal conversion from photoexcited singlet states 1(S1S0) to correlated triplet pair states 1(T1T1). We derive an expression for the internal conversion rate on the basis of the Fermi golden rule with an artificial Lorentzian broadening. The internal conversion rate depends on the interstate vibronic couplings (VCs) and energy difference (ΔESF) between 1(S1S0) and 1(T1T1). Therefore, understanding the interplay between interstate VCs and ΔESF is necessary to reveal how the structure-property relationship affects the SF efficiency. Here, we propose a method to quantitatively analyze interstate VCs between 1(S1S0) and 1(T1T1). We apply this method to SF in ortho-, meta-, and para-bis(ethynyltetracenyl)benzene and identify an effect of interstate VCs on the 1(T1T1) formation rate. The interstate VCs of the meta dimer are remarkably weak, which reasonably explains the experimentally obtained slow 1(T1T1) formation rate. The weak VCs result from a very small overlap density between 1(S1S0) and 1(T1T1) of the meta dimer. Furthermore, we investigate structure-dependence of the 1(T1T1) formation rate of the para dimer and find that the para dimer shows large VCs and small ΔESF when the rotational angle between the two tetracene units is large, which leads to the faster 1(T1T1) formation rate than those of the ortho and meta dimers. The rotation of the tetracene units is the origin of the experimentally observed fast 1(T1T1) formation rate of the para dimer.
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U2 - 10.1021/acs.jpca.0c03041
DO - 10.1021/acs.jpca.0c03041
M3 - Article
C2 - 32275421
AN - SCOPUS:85084379923
VL - 124
SP - 3641
EP - 3651
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
SN - 1089-5639
IS - 18
ER -