TY - JOUR
T1 - Impact of π-Conjugation Length on the Excited-State Dynamics of Star-Shaped Carbazole-π-Triazine Organic Chromophores
AU - Streater, Daniel
AU - Duisenova, Korlan
AU - Luo, Jian
AU - Kohlstedt, Kevin L.
AU - Zhang, Jian
AU - Huang, Jier
N1 - Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/6/2
Y1 - 2022/6/2
N2 - Correlating star-shaped donor-bridge-acceptor (DBA) molecular structures with intramolecular charge transfer (ICT) and intersystem crossing (ISC) is essential to their application in photocatalysis, photovoltaics, and organic light-emitting diodes (OLEDs). In this work, we report a systematic photophysical study on a series of star-shaped triazine-phenylene-carbazole DBA molecules with 0, 1, and 2 bridging phenylene units (pTCT-0P, pTCT-1P, pTCT-2P). Using a combination of steady-state and time-resolved spectroscopy with time-dependent density functional theory (TDDFT), we find that the bridge length can strongly impact the structural conformation, ICT, and ISC. Global target analysis of the time-resolved spectroscopy reveals that pTCT-0P has the most favorable ISC rate of 1.96 × 10-4ps-1, which is competitive with a singlet relaxation rate of 1.92 × 10-4ps-1. TDDFT aligns with spectroscopic results within an order of magnitude, predicting an ISC rate of 2.1 × 10-5ps-1and revealing that the donor/acceptor orthogonalization concomitantly suppresses singlet exciton recombination and lowers the singlet-triplet energy gap. The new fundamental insights gained from this work will help design the next generation of star-shaped DBA-type molecules for photocatalytic and photoelectronic applications.
AB - Correlating star-shaped donor-bridge-acceptor (DBA) molecular structures with intramolecular charge transfer (ICT) and intersystem crossing (ISC) is essential to their application in photocatalysis, photovoltaics, and organic light-emitting diodes (OLEDs). In this work, we report a systematic photophysical study on a series of star-shaped triazine-phenylene-carbazole DBA molecules with 0, 1, and 2 bridging phenylene units (pTCT-0P, pTCT-1P, pTCT-2P). Using a combination of steady-state and time-resolved spectroscopy with time-dependent density functional theory (TDDFT), we find that the bridge length can strongly impact the structural conformation, ICT, and ISC. Global target analysis of the time-resolved spectroscopy reveals that pTCT-0P has the most favorable ISC rate of 1.96 × 10-4ps-1, which is competitive with a singlet relaxation rate of 1.92 × 10-4ps-1. TDDFT aligns with spectroscopic results within an order of magnitude, predicting an ISC rate of 2.1 × 10-5ps-1and revealing that the donor/acceptor orthogonalization concomitantly suppresses singlet exciton recombination and lowers the singlet-triplet energy gap. The new fundamental insights gained from this work will help design the next generation of star-shaped DBA-type molecules for photocatalytic and photoelectronic applications.
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U2 - 10.1021/acs.jpca.2c00682
DO - 10.1021/acs.jpca.2c00682
M3 - Article
C2 - 35594508
AN - SCOPUS:85131268542
SN - 1089-5639
VL - 126
SP - 3291
EP - 3300
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 21
ER -