Chlorinated indium tin oxide as a charge injecting electrode for admittance spectroscopy

Admittance spectroscopy (AS) is a simple technique to measure the carrier mobility of organic semiconductors, but requires an Ohmic contact for charge injection. Chlorinated indium tin oxide (Cl-ITO) is shown to be a good charge injecting electrode for AS due to its high work function of >6.1 eV. The mobility of N,N'-diphenyl-N,N'-bis-(1-naphthyl)-1-1-biphenyl-4,4'-diamine (alpha-NPD) measured with Cl-ITO was found to be in excellent agreement with the value measured by time of flight. Cl-ITO is therefore an ideal electrode for AS since it possesses a high work function, but does not introduce any series impedance into the device structure. (C) 2011 Elsevier B.V. All rights reserved.