Abstract
We have investigated the hole injection characteristics from indium tin oxide (ITO) into a starburst amine, m-MTDATA, and have measured the hole carrier drift mobility of this compound in single-layer ITO/m-MTDATA/Au structures. We have found that ITO is able to provide trap-free space-charge-limited currents over a wide range of film thicknesses and have established unambiguously that the ITO/m-MTDATA is an ideal ohmic contact at high electric fields. The drift mobility of the m-MTDATA molecular glass was found to be electric field dependent, and a negative field dependence was detected at fields lower than 10 exp 5 V/cm. Our observations clarify the role of m-MTDATA as a voltage-lowering hole-injecting buffer layer in organic light-emitting diodes. (Author)