The density of states in thin film copper phthalocyanine measured by Kelvin probe force microscopy

The density of states (DOS) is an important factor in understanding charge transport in organic semiconductors. We use Kelvin probe force microscopy to find the DOS in thin films of copper phthalocyanine (CuPC). We find an exponential DOS with a characteristic energy of 0.11 eV over a 0.5 eV range of the highest occupied molecular orbital of CuPC. We also find that the technique is limited by charge trapping and hysteresis at low DOSs, and nonuniform potential profiles within the CuPC film at high DOSs. (c) 2008 American Institute of Physics.