Electronic properties of the organic semiconductor hetero-interface CUPc/C60

We present a study of the electronic properties of the interface between the well-established molecular organic semiconductor copper phthalocyanine (CuPc) and the fullerite C-60 using photoelectron spectroscopy and the Kelvin-probe (KP) method. Upon deposition of CuPc on C-60, we found interfacial shifts of the vacuum level indicating the formation of a dipole layer, while band bending is found to be negligible. The interface dipole of 0.5 eV measured with KP is close to the difference between the work functions of bulk CuPc and C-60. No evidence for a chemical interaction at the interface is concluded from the absence of additional features in the core-level spectra at the earliest stages of deposition. The energy-level alignment diagram at the CuPC/C-60 interface is derived. (c) 2005 Elsevier B.V. All rights reserved.