Graphene oxide/PEDOT:PSS as injection layer for quantum dot light emitting diode

We report a color-saturated, red quantum dot light-emitting diode (QD-LED) using graphene oxide doped PEDOT:PSS (PEDOT-GO) as the hole injection layer (HTL) to optimize the band offset between the HTL and emitting layers. As the doping concentration of the GO increases, the valence band of the PEDOT-GO down-shifts by 0.66 eV approaching that of the QDs. Meanwhile, the conductivity and transparency linearly changes as the doping concentration of GO increases. The QD-LEDs show a maximum luminance of up to 4200 cd/m2, corresponding to 7.5 lm/W in power efficiency and a turn-on voltage of 1.6 V. It is worth noting that the reduced turn-on voltage can be attributed to the direct exciton recombination within the QDs. Overall, there is a sixfold enhancement in the performance of the QD-LED with graphene oxide due to the higher hole injection/transfer rate and lower operating voltage