Transition metal oxides are being more frequently used as hole injection layer (HIL) in organic light emitting diodes (OLEDs), in place of polymer HILs such as PEDOT:PSS. The very thin films of the metal oxide HILs are usually deposited using vapor deposition, in order to create uniform films. Here, we report OLEDs fabricated using solution processed MoOx films as the HIL and super yellow as the emissive layer. The performance of the devices is comparable to PEDOT:PSS based devices, while the stability tests show the lifetime of MoOx-based devices is 4 106 h, about 40 times longer than PEDOT:PSS devices, at typical working condition. X-ray photoelectron spectroscopy (XPS) indicates both Mo5þ and Mo6þ states in the film. The Oxygen vacant MoO3 film shows bandgap states close to valence band, as confirmed by ultraviolet photoelectron spectroscopy and optical absorption. The method show promise for all-solutionprocessed LEDs utilizing metal oxide HILs.
