TY - JOUR
T1 - Triplet Energy Transfer Governs the Dissociation of the Correlated Triplet Pair in Exothermic Singlet Fission
AU - Lee, Tia S.
AU - Lin, Yunhui L.
AU - Kim, Hwon
AU - Pensack, Ryan D.
AU - Rand, Barry P.
AU - Scholes, Gregory D.
N1 - Publisher Copyright:
Copyright © 2018 American Chemical Society.
PY - 2018/7/19
Y1 - 2018/7/19
N2 - Singlet fission is a spin-allowed process of exciton multiplication that has the potential to enhance the efficiency of photovoltaic devices. The majority of studies to date have emphasized understanding the first step of singlet fission, where the correlated triplet pair is produced. Here, we examine separation of correlated triplet pairs. We conducted temperature-dependent transient absorption on 6,3-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn) films, where singlet fission is exothermic. We evaluated time constants to show that their temperature dependence is inconsistent with an exclusively thermally activated process. Instead, we found that the trends can be modeled by a triplet-triplet energy transfer. The fitted reorganization energy and electronic coupling agree closely with values calculated using density matrix renormalization group quantum-chemical theory. We conclude that dissociation of the correlated triplet pair to separated (but spin-entangled) triplet excitons in TIPS-Pn occurs by triplet-triplet energy transfer with a hopping time constant of approximately 3.5 ps at room temperature.
AB - Singlet fission is a spin-allowed process of exciton multiplication that has the potential to enhance the efficiency of photovoltaic devices. The majority of studies to date have emphasized understanding the first step of singlet fission, where the correlated triplet pair is produced. Here, we examine separation of correlated triplet pairs. We conducted temperature-dependent transient absorption on 6,3-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn) films, where singlet fission is exothermic. We evaluated time constants to show that their temperature dependence is inconsistent with an exclusively thermally activated process. Instead, we found that the trends can be modeled by a triplet-triplet energy transfer. The fitted reorganization energy and electronic coupling agree closely with values calculated using density matrix renormalization group quantum-chemical theory. We conclude that dissociation of the correlated triplet pair to separated (but spin-entangled) triplet excitons in TIPS-Pn occurs by triplet-triplet energy transfer with a hopping time constant of approximately 3.5 ps at room temperature.
UR - http://www.scopus.com/inward/record.url?scp=85049734372&partnerID=8YFLogxK
U2 - 10.1021/acs.jpclett.8b01834
DO - 10.1021/acs.jpclett.8b01834
M3 - Article
C2 - 29976063
AN - SCOPUS:85049734372
VL - 9
SP - 4087
EP - 4095
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 14
ER -