Space-charge-limited charge injection from indium tin oxide into a starburst amine and its implications for organic light-emitting diodes

Abstract

We have investigated the hole-injection characteristics from indium tin-oxide (ITO) into 4,4′,4 ″-trisN,-(3-methylphenyl)-N-phenylaminotriphenylamine (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. Our observations clarify the role of m-MTDATA as a voltage-lowering hole-injecting buffer layer in organic light-emitting diodes. © 1998 American Institute of Physics.