Direct observation of ICT cations at the HTL/transparent semiconductor interface

The cation density at the interface of a transparent anode and an organic layer has been measured for several hole transport (HT) materials. The number of cations at the interface of ITO:MoOx with rubrene, NPB, m-MTDATA and TCTA was found to range from 8 x 10(13) to 1.5 x 10(14) per cm(2) in freshly prepared devices. These values decreased by about 25% after one month. These cations are part of the dipole layer that results from the transfer of electrons from an organic layer, whose adiabatic ionization potential is less than the work function of the anode. (C) 2014 Elsevier B.V. All rights reserved.