Large Performance Enhancement in All-Solution-Processed, Full-Color, Inverted Quantum-Dot Light-Emitting Diodes Using Graphene Oxide Doped Hole Injection Layer

Solution-processed hole-injection layers (HILs) for full-color, inverted quantum-dot light-emitting diodes (QLEDs) are developed by simply incorporating the graphene oxide (GO) into poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PE-DOT:PSS). The excellent wettability of the GO-doped PE-DOT:PSS mixture facilitates the effective deposition of HIL onto the organic underlayer. Ultraviolet photoelectron spectroscopy and Raman spectroscopy characterization reveal that the GO-doped PEDOT:PSS HIL possesses the advantages of increased work function and improved conductivity. Thus, the GO-doped PEDOT:PSS HIL can promote hole injection from the top anode into the device by reducing the hole-injection barrier and sheet resistance. As a result, using the GO-doped PEDOT:PSS HIL, we have successfully demonstrated highly bright all-solution-processed, full-color, inverted QLEDs showing remarkably enhanced luminance of 142 165, 63 318, and 3019 cd/m(2) for green, red, and blue devices, respectively. To the best of our knowledge, the green device's luminance is the best for all-solution-processed inverted green QLEDs. These results suggest that the GO-doped PEDOT:PSS is a promising candidate for high-quality HIL in all-solution-processed QLEDs with an inverted structure.