Sai N, Gearba R, Dolocan A, Tritsch JR, Chan WL, Chelikowsky JR, Leung K, Zhu X. Understanding the Interface Dipole of Copper Phthalocyanine (CuPc)/C60: Theory and Experiment.
J Phys Chem Lett 2012;
3:2173-2177. [PMID:
26295767 DOI:
10.1021/jz300744r]
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Abstract
Interface dipole determines the electronic energy alignment in donor/acceptor interfaces and plays an important role in organic photovoltaics. Here we present a study combining first principles density functional theory (DFT) with ultraviolet photoemission spectroscopy (UPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) to investigate the interface dipole, energy level alignment, and structural properties at the interface between CuPc and C60. DFT finds a sizable interface dipole for the face-on orientation, in quantitative agreement with the UPS measurement, and rules out charge transfer as the origin of the interface dipole. Using TOF-SIMS, we show that the interfacial morphology for the bilayer CuPc/C60 film is characterized by molecular intermixing, containing both the face-on and the edge-on orientation. The complementary experimental and theoretical results provide both insight into the origin of the interface dipole and direct evidence for the effect of interfacial morphology on the interface dipole.
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