Efficient Quantum Dot Light-Emitting Diodes Based on Trioctylphosphine Oxide-Passivated Organometallic Halide Perovskites

Metal halide perovskite quantum dots (QDs) have attracted significant research interest in the next-generation display and solid illumination fields due to their excellent optical properties of high photoluminescence quantum efficiency, high color purity, obvious quantum confinement effect, and large exciton binding energy. A large amount of surface defects and nonradiative recombination induced by these defects are considered as major problems to be resolved urgently for practical applications of perovskite QDs in high-efficiency light-emitting diodes (LEDs). Herein, we report an efficient passivation of green perovskite QD CH₃NH₃PbBr₃ with trioctylphosphine oxide (TOPO). By simply adding the appropriate amount of TOPO into the nonpolar toluene solvent to synthesize CH₃NH₃PbBr₃ QDs, the surface defects of these as-synthesized perovskite QDs are obviously reduced, along with an increased photoluminescence lifetime and suppressed nonradiative recombination. Further investigation indicates that electronegative oxygen from TOPO (Lewis base) bonds with uncoordinated Pb²⁺ ions and labile lead atoms in perovskite. With TOPO passivation, the green perovskite QD LEDs based on CH₃NH₃PbBr₃ show significant performance improvement factors of 93.5, 161.1, and 168.9% for luminance, current efficiency, and external quantum efficiency, respectively, reaching values of 1635 cd m^-2, 5.51 cd A^-1, and 1.64% in the eventual optimized devices. Furthermore, the presence of TOPO dramatically improves stabilities of CH₃NH₃PbBr₃ QDs and related devices. Our work provides a robust platform for the fabrication of low-defect-density perovskite QDs and efficient, stable perovskite QD LEDs.