Electronic structure near the Fermi level of the organic semiconductor copper phthalocyanine

The electronic structure of thin films of the prototypical organic semiconductor copper phthalocyanine (CuPc) has been measured using resonant soft X-ray emission spectroscopy. We report the observation of two discrete states near EF. This differs from published photoemission results, but is in excellent agreement with density functional calculations. The implications of this result for the use of resonant soft X-ray emission (SXE) in the study of organic semiconductors are discussed. We also compare our data to published X-ray emission results, and show that the latter display clear evidence of beam damage.