High-Performance perovskite quantum dots light-emitting diodes with hole transport layer engineering and synergetic outcoupling enhancement

Perovskite quantum dot light-emitting diodes (PeQLEDs) are frequently considered as the most promising alternatives to organic light-emitting diodes (OLEDs). However, the efficiency of PeQLEDs remains inferior to OLEDs due to suboptimal charge carrier transport and intrinsic light outcoupling efficiency (η_out). Herein, a combination of hole transport layer (HTL) engineering and substrate engineering is demonstrated to improve the charge injection and η_out of PeQLEDs. To replace the conventional PEDOT:PSS, a novel HTL bilayer based on modified PEDOT:PSS and PVK with a lower refractive index and fewer trap densities at the HTL-QDs interface is developed. Additionally, this study identifies the ideal thickness of ITO for achieving optimal η_out of PeQLEDs through optical simulations and experimental validation. Based on the synergistic use of HTL bilayer and 70-nm-thick ITO, the PeQLEDs achieved an optimal external quantum efficiency of 17.96 % at a luminance of 1763 cd/m² and 15.19 % at 8300 cd/m² without using any external outcoupling structure, indicating a low efficiency roll-off.