Aluminum-Modified Molybdenum Trioxide for Electron Injection in Inverted Organic Light-Emitting Diodes

Electron injection using ambient stable electrodes is essential for organic light-emitting diodes (OLEDs), particularly for the bottom electrode of the inverted OLEDs. Here, a metal-oxide-based highly transparent electron injection layer (EIL) is proposed. This metal-oxide-based EIL consists of thin layer of aluminum (Al)-modified molybdenum trioxide (MoO3). It is demonstrated that the surface of the MoO3 layer can be chemically reduced by a very thin overlayer of Al (1 nm), resulting in a lower effective surface work function as well as introducing a number of gap states in the reduced molybdenum oxide layer. With this surface Al-doped MoO3 EIL, efficient inverted OLEDs are demonstrated over typical conductive electrodes such as indium tin oxide (ITO) and poly(3,4-ethylenedioxythio-phene): poly(styrenesulfonate) (PEDOT:PSS).