Ultrafast Charge Generation in an Organic Bilayer Film.
The dynamics of charge generation in a high performing molecular photovoltaic system, p-SIDT(FBTTh2)2 (see Figure 1 ) is studied with transient absorption. The optimized bulk heterojunction material shows behavior observed in many other systems; the majority of charges are generated at short time scales (<150 fs), and a slower contribution from incoherently diffusing excitons is observed at low pump fluence. In a separate experiment, the role of bulk heterojunction material morphology on the process of ultrafast charge generation was investigated with bilayers made with solution processed donor molecules on a photopolymerized C60 layer. The majority of carriers are again produced at short time scales, ruling out the idea that subpicosecond charge generation can be understood wholly in terms of localized excitons. We evaluate possible causes of this behavior and propose that the excited state is highly delocalized on short time scales, providing ample probability density at the charge generating interface.
†Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106-5090, United States.
Loren G
LG
Kaake
†Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106-5090, United States.|‡Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510640 People's Republic of China.
Chengmei
C
Zhong
†Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106-5090, United States.
John A
JA
Love
§Functional Materials Chemistry Group, Polymer Materials Unit National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
Ikuhiro
I
Nagao
†Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106-5090, United States.|∥Department of Chemistry, University of California, Santa Barbara, California, 93106-9510, United States.
Guillermo C
GC
Bazan
†Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106-5090, United States.|∥Department of Chemistry, University of California, Santa Barbara, California, 93106-9510, United States.|⊥Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 22254, Saudi Arabia.
Thuc-Quyen
TQ
Nguyen
‡Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510640 People's Republic of China.
Fei
F
Huang
‡Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, 510640 People's Republic of China.
Yong
Y
Cao
†Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106-5090, United States.
Daniel
D
Moses
†Center for Polymers and Organic Solids, University of California, Santa Barbara, California 93106-5090, United States.|§Functional Materials Chemistry Group, Polymer Materials Unit National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.|#Department of Physics, University of California, Santa Barbara, California, 93106-9530, United States.
Alan J
AJ
Heeger
Charge Transfer; Energy Transport; Exciton Dynamics; Organic Photovoltaic; Transient Absorption