Synergistic effects of Li-doped NiOx film prepared by low-temperature combustion as hole-injection layer for high performance OLED devices

The hole-injection layer (HIL) has vital impacts on the electroluminescence performance of organic light-emitting diodes (OLEDs). Herein, low-temperature solution-processed Li-doped nickel oxide (Li:NiO x ) was fabricated as a novel HIL for OLEDs. As a result, the phosphorescent green OLED with 5% molar ratio Li:NiO x exhibits the best performance with low turn-on voltage of 3.1 V, maximum current efficiency of 55.8 cd A −1 , maximum power efficiency of 57.2 lm·W −1 and maximum external quantum efficiency of 17.1%. While it is only 52.1 cd A −1 , 50.9 lm·W −1 and for the reference device with undoped NiO x film, corresponding a 7%, 12% and 8% enhancement in efficiency respectively . It reveals that the improved efficiency of the Li:NiO x film HIL based device with is mainly ascribed to the synergistic effect of extrinsic doping in the aspects of achieving enhanced hole injection. Our work demonstrates that the solution-processed Li-doped NiO x film is a promising HIL for high-performance OLEDs.