TY - JOUR
T1 - Theory of Transient Excited State Absorptions in Pentacene and Derivatives
T2 - Triplet-Triplet Biexciton versus Free Triplets
AU - Khan, Souratosh
AU - Mazumdar, Sumit
N1 - Funding Information:
We acknowledge support from the University of Arizona’s REN Faculty Exploratory Research Grant and from Arizona TRIF Photonics. We are grateful to Dr. A. Rao for sending the experimental data from which the experimental absorption spectrum of Figure 2a was constructed. We are also grateful to Drs. Alok Shukla, J. Clark, A. Musser, R. Pensack, and A. Rao for extensive discussions and to R. Pensack and C. Grieco for making unpublished data available.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/12/7
Y1 - 2017/12/7
N2 - Recent experiments in several singlet-fission materials have found that the triplet-triplet biexciton either is the primary product of photoexcitation or has a much longer lifetime than believed until now. It thus becomes essential to determine the difference in the spectroscopic signatures of the bound triplet-triplet and free triplets to distinguish between them optically. We report calculations of excited state absorptions (ESAs) from the singlet and triplet excitons and from the triplet-triplet biexciton for a pentacene crystal with the herringbone structure and for nanocrystals of bis(triisopropylsilylethynyl) (TIPS)-pentacene. The triplet-triplet biexciton absorbs in both the visible and the near-infrared (NIR), while the monomer free triplet absorbs only in the visible. The intensity of the NIR absorption depends on the extent of intermolecular coupling, in agreement with observations in TIPS-pentacene nanocrystals. We predict additional weak ESA from the triplet-triplet but not from the triplet, at still lower energy.
AB - Recent experiments in several singlet-fission materials have found that the triplet-triplet biexciton either is the primary product of photoexcitation or has a much longer lifetime than believed until now. It thus becomes essential to determine the difference in the spectroscopic signatures of the bound triplet-triplet and free triplets to distinguish between them optically. We report calculations of excited state absorptions (ESAs) from the singlet and triplet excitons and from the triplet-triplet biexciton for a pentacene crystal with the herringbone structure and for nanocrystals of bis(triisopropylsilylethynyl) (TIPS)-pentacene. The triplet-triplet biexciton absorbs in both the visible and the near-infrared (NIR), while the monomer free triplet absorbs only in the visible. The intensity of the NIR absorption depends on the extent of intermolecular coupling, in agreement with observations in TIPS-pentacene nanocrystals. We predict additional weak ESA from the triplet-triplet but not from the triplet, at still lower energy.
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U2 - 10.1021/acs.jpclett.7b02748
DO - 10.1021/acs.jpclett.7b02748
M3 - Article
C2 - 29164900
AN - SCOPUS:85037715630
VL - 8
SP - 5943
EP - 5948
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
SN - 1948-7185
IS - 23
ER -