Stable and Efficient Pure‐Red Perovskite Light‐Emitting Diodes

The bromine/iodine mixed halide perovskites have been extensively employed for pure-red emission. However, the issues of compositional heterogeneity and halide ion migration result in impure emission and compromised stability and efficiency for the perovskite light-emitting diodes (PeLEDs). Herein, a novel approach is proposed by incorporating multi-functional graphene quantum dots (GQDs) into the perovskites to address these critical problems. The new principles of composition reconstruction, perovskite phase isolation, and halide ion immobilization are revealed to address the unique and synergistic role of GQDs in achieving homogeneous perovskite films and suppressing halide ion migration, and clarify the formation of strong coordination and hydrogen bonding interaction between GQDs and the perovskites. As a result, high-performance pure-red PeLEDs that showcase a fantastic efficiency of 27.9% with a narrow emission at 640 nm and a remarkable lifetime of 110.3 h with consistently stable EL spectra during tests, representing one of the best-performing pure-red PeLEDs, are demonstrated. This strategy contributes an effective approach to solve the critical concerns in mixed-halide perovskites for stable and efficient pure-red PeLEDs for the community.