It is still challenging to achieve high-efficiency pure-red (620-650 nm wavelength) perovskite light-emitting diodes (PeLEDs). Herein, we report pure-red PeLEDs with Commission Internationale de l'Eclairage coordinates (0.703, 0.297) meeting the Rec. 2020, an external quantum efficiency of 20.8%, and a luminance of 3775 cd/m2. This design is based on the strong quantum confinement CsPbI3 quantum dots (QDs) capped by composite ligands of 3-phenyl-1-propylamine and tetrabutylammonium iodide. This strategy stabilized the structure of the strong-confined QDs and reduced the influence of the electric field-induced Stark effect on the PeLEDs. Furthermore, the exciton binding energy of the QDs was decreased by the composited ligands to suppress Auger recombination within the devices. Additionally, the valence-band maximum of the QDs was lifted to match the hole-transport layer, thus balancing charge injection in the PeLEDs. Our device also demonstrated a stable electroluminescence spectrum and a lifetime of 5.6 times longer than the control device.
Keywords: high efficiency; perovskite light-emitting diodes; pure-red emission; quantum confinement; quantum dots.