MoO₃-induced oxidation doping of PEDOT:PSS for high performance full-solution-processed inverted quantum-dot light emitting diodes

Full-solution processed inverted quantum dot light-emitting diodes (QD-LEDs) are promising candidates for application in next generation active matrix displays, due to their low-cost solution fabrication processes and easy integration with n-type thin-film transistor backplanes. In this work, we report high performance transparent inverted QD-LEDs using a full-solution processable hybrid composite anode, formulated using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), solution-processed molybdenum trioxide (s-MoO₃), and silver nanowires. The effect of the aqueous s-MoO₃ additive in the PEDOT:PSS anode on efficient operation of the QD-LEDs was systematically investigated. Our results show that the s-MoO₃ additive not only enhances the wettability of the PEDOT:PSS surface, but also improves the conductivity of the PEDOT:PSS layer, leading to an ohmic contact between the composite anode and the hole transporting layer for efficient hole injection. With an optimal s-MoO₃ addition in the PEDOT:PSS anode, the full-solution processable inverted QD-LEDs with a maximum current efficiency of 1.39 cd A^-1 and a visible light transparency of over 70% were demonstrated. The composite transparent anode enables a 27% increase in current efficiency of the full-solution processable QD-LEDs compared to that of the structurally identical control device without the s-MoO₃ additive. The encouraging results suggest that our investigation paves the way for the development of efficient vacuum-free transparent inverted QD-LEDs.