RT Journal Article
SR Electronic
T1 Intermolecular vibrations mediate ultrafast singlet fission
JF Science Advances
JO Sci Adv
FD American Association for the Advancement of Science
SP eabb0052
DO 10.1126/sciadv.abb0052
VO 6
IS 38
A1 Duan, Hong-Guang
A1 Jha, Ajay
A1 Li, Xin
A1 Tiwari, Vandana
A1 Ye, Hanyang
A1 Nayak, Pabitra K.
A1 Zhu, Xiao-Lei
A1 Li, Zheng
A1 Martinez, Todd J.
A1 Thorwart, Michael
A1 Miller, R. J. Dwayne
YR 2020
UL http://advances.sciencemag.org/content/6/38/eabb0052.abstract
AB Singlet fission is a spin-allowed exciton multiplication process in organic semiconductors that converts one spin-singlet exciton to two triplet excitons. It offers the potential to enhance solar energy conversion by circumventing the Shockley-Queisser limit on efficiency. We study the primary steps of singlet fission in a pentacene film by using a combination of TG and 2D electronic spectroscopy complemented by quantum chemical and nonadiabatic dynamics calculations. We show that the coherent vibrational dynamics induces the ultrafast transition from the singlet excited electronic state to the triplet-pair state via a degeneracy of potential energy surfaces, i.e., a multidimensional conical intersection. Significant vibronic coupling of the electronic wave packet to a few key intermolecular rocking modes in the low-frequency region connect the excited singlet and triplet-pair states. Along with high-frequency local vibrations acting as tuning modes, they open a new channel for the ultrafast exciton transfer through the resulting conical intersection.