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 (Re O3) -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 Re O3 -doped NPB HTL exhibit driving voltage of 5.2-5.4 V and power efficiency of 2.2-2.3 lmW at 20 mA cm2, which is significantly improved compared to those (7.1 V and 2.0 lmW, respectively) obtained from the devices with undoped NPB. Furthermore, the device with Re O3 -doped NPB layer reveals the prolonged lifetime than that with undoped NPB. Details of Re O3 doping effects are described based on the UV-Vis absorption spectra and characteristics of hole-only devices.