A new diamine as the hole-transporting material for organic light-emitting diodes

A new diamine, N,N?-diphenyl-N,N?-bis-biphenyl-(1,1?-biphenyl)-4,4?-diamine (PTPD), has been synthesised to be applied as a hole-transporting material for multilayer organic light-emitting diodes (LEDs). Electrical and optical characteristics of a series of double-layer (DL) LEDs using PTPD as hole-transporting layers (HTL) and Alq3 and Znq2 as electron-transporting layers have been measured and compared with those for DL LEDs based on other HTLs (TPD and NTPD). The differences are discussed in terms of charge injection at the electrodes and electron-hole recombination processes at the organic interfaces. The prerequisites based on the molecular structure of the compound, confirmed by preliminary experimental observations, suggest PTPD to be a stable hole-transporting material for high-durability organic LEDs. Copyright © 2000 John Wiley & Sons, Ltd.