Ultrafast Electron Transfer at Organic Semiconductor Interfaces: Importance of Molecular Orientation.
Much is known about the rate of photoexcited charge generation in at organic donor/acceptor (D/A) heterojunctions overaged over all relative arrangements. However, there has been very little experimental work investigating how the photoexcited electron transfer (ET) rate depends on the precise relative molecular orientation between D and A in thin solid films. This is the question that we address in this work. We find that the ET rate depends strongly on the relative molecular arrangement: The interface where the model donor compound copper phthalocyanine is oriented face-on with respect to the fullerene C60 acceptor yields a rate that is approximately 4 times faster than that of the edge-on oriented interface. Our results suggest that the D/A electronic coupling is significantly enhanced in the face-on case, which agrees well with theoretical predictions, underscoring the importance of controlling the relative interfacial molecular orientation.
†Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.|‡Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
Alexander L
AL
Ayzner
‡Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
Dennis
D
Nordlund
§Department of Organic Materials and Fiber Engineering, Soongsil University, Seoul, 156-743 Korea.
Do-Hwan
DH
Kim
†Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.
Zhenan
Z
Bao
‡Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
Michael F
MF
Toney
charge-transfer state; core-hole clock; electron dynamics; organic photovoltaic; resonant Auger; resonant photoemission