Impact of Intermolecular Distance on Singlet Fission in a Series of TIPS Pentacene Compounds.
Singlet fission has attracted considerable interest for its potential application in organic photovoltaics. However, the underlying microscopic mechanism is not well understood and the molecular parameters that govern SF efficiency remain unclear. We herein study the primary exciton photogeneration and evolution in the thin film of a series of pentacene derivatives (TIPS-Pn and ADPD-Pn) using femtosecond transient absorption spectroscopy. With a favorable "long-edge on" packing motif, the singlet-excited slip-stacked TIPS-Pn and ADPD-Pn molecules undergo ultrafast fission to produce triplet excitonic states with time constants of ∼0.3 ps. More importantly, the ADPD-Pn compound features a considerably higher triplet yield than TIPS-Pn (162 ± 10% vs 114 ± 15%). The enhanced electronic coupling as a result of closer interchromophore distance (3.33 Å for ADPD-Pn vs 3.40 Å for TIPS-Pn) is suggested to account for the much higher triplet yield for ADPD-Pn relative to that for TIPS-Pn, proving SF can be readily modulated by adjusting the intermolecular distance.
†Beijing National Laboratory for Molecules Science (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, and Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
Yishi
Y
Wu
‡State Key Laboratory of Applied Organic Chemistry (SKLAOC), College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People's Republic of China.
Ke
K
Liu
†Beijing National Laboratory for Molecules Science (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, and Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
Huiying
H
Liu
†Beijing National Laboratory for Molecules Science (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, and Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
Yi
Y
Zhang
‡State Key Laboratory of Applied Organic Chemistry (SKLAOC), College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People's Republic of China.
Haoli
H
Zhang
†Beijing National Laboratory for Molecules Science (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, and Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
Jiannian
J
Yao
†Beijing National Laboratory for Molecules Science (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, and Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.|§Beijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, People's Republic of China.
Hongbing
H
Fu
Intermolecular coupling; Molecular orientation; Pentacene; Singlet fission; Transient absorption spectroscopy