Facile solution-processed aqueous MoO^sub x^ for feasible application in organic light-emitting diode

Solution-processed techniques attract increasing attentions in organic electronics for their low-cost and scalable manufacturing. We demonstrate the favorite hole injection material of solution-processed aqueous MoOx (s-MoOx) with facile fabrication process and cast successful application to constructing efficient organic light-emitting diodes (OLEDs). Atomic force microscopy and X-ray photoelectron spectroscopy analysis show that s-MoOx behaves superior film morphology and non-stoichiometry with slight oxygen deficiency. With tris(8-hydroxy-quinolinato) aluminium as emitting layer, s-MoOx based OLED shows maximum luminous efficiency of 7.9 cd/A and power efficiency of 5.9 lm/W, which have been enhanced by 43.6% and 73.5%, respectively, in comparison with the counterpart using conventional vacuum thermal evaporation MoOx. Current-voltage, impedance-voltage, phase-voltage and capacitance-voltage characteristics of hole-only devices indicate that s-MoOx with two processes of "spin-coating/annealing" shows mostly enhanced hole injection capacity and thus promoting device performance. Our experiments provide an alternative approach for constructing efficient OLED with solution process.