ABSTRACT

 Perovskite quantum dot light-emitting diodes (PeQLEDs) are frequently considered as the ideal organic light-emitting diodes (OLEDs) alternatives. However, the efficiency of PeQLEDs remains inferior to OLEDs because their charge carrier transport and intrinsic light outcoupling efficiency (ηout) are not optimized. To improve the charge injection and ηout of PeQLEDs, synergistic hole transport layer (HTL) engineering and substrate engineering are demonstrated herein. The HTL bilayer (modified PEDOT:PSS and PVK) exhibits a lower refractive index, reduced surface roughness, and fewer trap densities at the HTL-QDs interface. For substrate engineering, the ideal thickness of ITO to realize optimal ηout of PeQLEDs is identified by both optical simulations and experimental verification. With the incorporation of HTL bilayer and 70-nm-thick ITO, the PeQLEDs achieved an external quantum efficiency of 17.96% at a luminance of 1763 cd m-2 and 15.19% at 8300 cd m-2 without using any external outcoupling structure, indicating a low efficiency roll-off.