Low driving voltage and high stability organic light-emitting diodes with rhenium oxide-doped hole transporting layer

The authors report a promising metal oxide-doped hole transporting layer (HTL) of rhenium oxide (ReO3)-doped N,N '-diphenyl-N,N-'-bis (1,1 '-biphenyl)-4,4 '-diamine (NPB). The tris(8-hydroxyquinoline) aluminum-based organic light-emitting diodes with ReO3-doped NPB HTL exhibit driving voltage of 5.2-5.4 V and power efficiency of 2.2-2.3 lm/W at 20 mA/cm(2), which is significantly improved compared to those (7.1 V and 2.0 lm/W, respectively) obtained from the devices with undoped NPB. Furthermore, the device with ReO3-doped NPB layer reveals the prolonged lifetime than that with undoped NPB. Details of ReO3 doping effects are described based on the UV-Vis absorption spectra and characteristics of hole-only devices. (c) 2007 American Institute of Physics.