Organic light-emitting diodes (OLEDs) have attracted huge attention because of their increasing application in high-quality flat-panel displays and potential utilization in energy-efficient solid-state lighting sources. High-efficiency is always a crucial concern for OLED devices being energy-saving and to have a longer life-span. OLEDs have encountered enormous difficulties in meeting the high-performance, low-cost requirements for large-sized OLED devices due to a major limitation in vacuum thermal evaporation technology. Therefore, a solution process has drawn a considerable amount of attention as an alternative for production because it allows low-cost, large-area processing. In a multilayer OLED, the quality of the hole injection layer is a crucial factor for the operating voltage, power efficiency, and stability of the device. Transition metal oxides have shown great potential owing to their wide range of possible energy level alignments and charge balance. In this study, we report a low-temperature solution-processed hybrid metal oxide MoO3-WO3 hole injection/transport layer (HIL/HTL) for high-efficiency organic light-emitting diodes. The electroluminescence characteristics of hybrid MoO3-WO3 and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) based devices were studied with the structure ITO/MoO3:WO3 or PEDOT:PSS/CBP:Ir(2-phq)3/TPBi/LiF/Al. The MoO3-WO3-based OLEDs displayed relatively much higher device performance and low roll-off than that of the counter PEDOT:PSS in terms of a maximum luminance of 20,370 cd m-2, power efficiency of 27.7 lm W-1, external quantum efficiency (EQE) of 8.7% and, more importantly, low turn-on voltage of 2.1 V with the CIE of (0.55, 0.45). PEDOT:PSS based devices showed a poor power efficiency, maximum luminance and turn-on voltage of 14.6 lm W-1, 6765 cd m-2 and 3.5 V, respectively. The hybrid metal oxides HIL/HTL has lead to a significantly reduced energy-barrier for both hole and electron to transport, revealed by the relatively low driving voltage and low roll-off. This demonstration of a bright, energy-efficient and stable MoO3/WO3-based OLED provides a feasible application of solution-processable transition metal oxide materials as the HIL/HTL within OLEDs and promotes the development of low-cost high-efficiency, all-solution-processed optoelectronic devices. These are the highest power efficacies ever reported for this particular device architecture.