Highly Efficient Sky‐Blue Perovskite Quantum Dot Light‐Emitting Diodes via Ligand‐Assisted Trap‐State Passivation

Lead‐halide perovskite quantum dots (QDs) have garnered considerable attention in the field of light‐emitting diodes (LEDs) due to their extraordinary optoelectronic properties. However, it is still difficult to fabricate blue LEDs with high efficiency, due to the surface trap‐mediated non‐radiative charge recombination from unstable emitters. Herein, short‐chain ligand tridecylamine (TDA) is introduced as a surface passivation strategy to synthesize high‐performance sky‐blue CsPbBr 3 QDs via size engineering, which show a stable photoluminescence (PL) intensity with a higher PL quantum yield (PLQY). This improvement is achieved through well‐suppressed surface defects by the ligand TDA with stronger affinity, resulting in the reduced non‐radiative recombination due to trap‐state passivation. Consequently, high‐efficiency sky‐blue QD LEDs were fabricated, which presented a peak EQE of 13.6% at 492 nm. Our findings suggest that this feasible surface modification approach can alter carrier dynamics and facilitate charge injection balance to develop stable and efficient perovskite LEDs.