Multifunctional-Ligand Enabled Stable CsPbI₃ Quantum Dots for Highly Efficient Pure-Red Light-Emitting Diodes

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• High-performance pure-red perovskite light-emitting diodes (PeLEDs) show promise for optoelectronics.
• Instability and poor performance of perovskite quantum dots (QDs) hinder commercialization.
• Surface defects and insulating ligands limit QD stability and efficiency.

Purpose of the Study:

• To synthesize highly stable red CsPbI3 QDs using a novel additive ligand.
• To improve the surface passivation and photophysical properties of red CsPbI3 QDs.
• To enhance the performance of pure-red PeLEDs through QD surface modification.

Main Methods:

• Introduction of phenformin hydrochloride (PhenHCl) as a multifunctional additive ligand.
• Utilizing the biguanide functional group for hydrogen bonding with lead halide octahedra.
• Employing excess Cl- anions to compensate for iodine vacancies and eliminate trap states.

Main Results:

• Achieved a photoluminescence quantum yield (PLQY) of 98.6% for red CsPbI3 QDs.
• Demonstrated excellent ambient stability with 90% PL intensity retention over 80 days.
• Developed pure-red PeLEDs with an external quantum efficiency (EQE) of 13.38% and a maximum luminance of 2159 cd m-2 at 649 nm.

Conclusions:

• Phenformin hydrochloride effectively passivates surface defects in CsPbI3 QDs through synergistic effects.
• The modified QDs exhibit significantly enhanced stability and photoluminescence properties.
• This approach offers a viable strategy for improving the performance of pure-red PeLEDs for advanced optoelectronic applications.