Significance of irreversible formation of "electromer'' in 1-bis[4-[N,N-di(4-tolyl)amino]phenyl]-cyclohexane layer associated with the stability of deep blue phosphorescent organic light emitting diodes

Abstract

We demonstrate that injection of electrons in 1-bis[4-[N,N-di(4-tolyl)amino]phenyl]-cyclohexane (TAPC) layer irreversibly induces defect sites responsible for "electromer'' emission. We also show that the defects alter the charge transporting properties of TAPC layer to influence the charge balance of iridium(III)[bis(4,6-difluorophenyl)pyridinato-N,C-2 ']tetrakis(1-pyrazolyl)borate (FIr6) based deep blue phosphorescent organic light emitting diodes (PHOLED). The present investigation implies that deep-blue PHOLEDs should be carefully designed for the emission zone to be located far enough from the TAPC layer so as to avoid or minimize the emission from TAPC layer. (c) 2012 Elsevier B.V. All rights reserved.