Tuning the interfacial hole injection barrier between p-type organic materials and Co using a MoO 3 buffer layer

Abstract

We demonstrate that the interfacial hole injection barrier Δ h between p-type organic materials (i.e., CuPc and pentacene) and Co substrate can be tuned by the insertion of a MoO 3 buffer layer. Using ultraviolet photoemission spectroscopy, it was found that the introduction of MoO 3 buffer layer effectively reduces the hole injection barrier from 0.8 eV to 0.4 eV for the CuPc/Co interface, and from 1.0 eV to 0.4 eV for the pentacene/Co interface, respectively. In addition, by varying the thickness of the buffer, the tuning effect of Δ h is shown to be independent of the thickness of MoO 3 interlayer at both CuPc/Co and pentacene/Co interfaces. This Fermi level pinning effect can be explained by the integer charge-transfer model. Therefore, the MoO 3 buffer layer has the potential to be applied in p-type organic spin valve devices to improve the device performance via reducing the interfacial hole injection barrier. © 2012 American Institute of Physics.