Solution-processed MoOx hole injection layer towards efficient organic light-emitting diode

Low cost, high throughout and large scale production techniques, such as roll-to-roll, printing and doctor blading, boost the favorite of electronic devices with all solution process. While MoOx are conventionally formed via high temperature and vacuum deposition, we develop a novel, lower-temperature, solution-processable MoOx hole injection layer (HIL) and cast successful application in organic light-emitting diodes (OLEDs). The characterization of MoOx is presented in detail using X-ray diffraction, atomic force microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and impedance spectroscopy measurements. The results show MoOx features amorphous phase structure, superior film morphology and exceptional electronic properties. With solution-processed MoOx as HIL, highly efficient OLED is demonstrated. The luminous efficiency has been enhanced by 56% in comparison with that of the counterpart using evaporated MoOx. The main reasons for the substantially improved performance are the tailored surface work function and appropriate hole injection capacity correspondingly result in optimizing carrier balance in OLED. Our results pave a way for advancing MoOx-based organic electronic devices with solution-processable techniques.