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 5.2–5.4V and power efficiency of 2.2–2.3lm∕W at 20mA∕cm2, which is significantly improved compared to those (7.1V and 2.0lm∕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.