Amino Acid-Passivated Pure Red CsPbI3 Quantum Dot LEDs

Quantum-confined CsPbI3 nanocrystals (NCs) are promising materials for the next generation of pure-red displays. Small quantum dots synthesized by colloidal methods often have excess resistive ligands, which reduce the efficiency and long-term stability of the resulting light-emitting diodes (LEDs). Here we developed a facile ligand-exchange method using amino acids to reduce long chain ligands on CsPbI3 quantum dots and improve the efficiency and stability of LEDs made from these QDs. We also assessed a variety of related amino acids and noted how their structure affects the LED performance. We found that a dual-passivation effect was observed in cysteine-passivated QDs that led to the best performance. The optimized LEDs achieved an external quantum efficiency (EQE) of 18.0% and a T-50 of 87 min, comparable with many of the best reported perovskite QD, pure red LEDs.