Stable and Efficient Red InP-Based QLEDs through Surface Passivation Strategies of Quantum Dots

Indium phosphide (InP) is a representative of environmentally friendly quantum dots (QDs), and quantum dot light-emitting diodes (QLEDs) based on InP QDs are prime candidates for next-generation display applications. However, there are numerous nonradiative sites on the surface of InP QDs, which compromise the operational stability of QLEDs. Herein, we employed cysteamine (CTA) molecules for post-treatment of QD films, effectively passivating surface defects and nonradiative sites, thereby enhancing stability. This treatment enabled a long T₉₅ lifetime of over 1,200 h at an initial luminance of 1,000 cd m^-2. Additionally, CTA-treated QDs induced the formation of an interface dipole, elevating the energy levels of QDs and reducing the injection barrier for holes. Moreover, the dipole moment at the interface hindered electron injection, achieving a more balanced carrier injection in the device. Consequently, we achieved a peak external quantum efficiency (EQE) of 21.21%.