Insights into ligand passivation strategies for multiple types of surface defects in high-performance perovskite quantum dot light-emitting diodes

Abstract

Perovskite quantum dots (PeQDs) have attracted increasing attention for light-emitting diode applications owing to their excellent optoelectronic properties. However, they possess many crystalline defects, leading to degradation of their emissive performance, which is mainly attributed to ligand desorption from the surface of the quantum dots during their purification with polar solvents. Here, the influence of post-treatment strategies on the performance of PeQDs was systematically investigated, and further, a dual-site anchoring strategy based on the zwitterionic molecule 3-NDS is proposed to stabilize their dynamic surface. In terms of systematic experiments and theoretical calculations, the mechanism of ligand rearrangement on the surface of the quantum dots during their purification is elucidated. 3-NDS, by means of strong anchoring through its (CH₂)₂N(CH₃)⁺ and SO₃⁻ functional groups, substantially reduces surface defects in quantum dots and the corresponding perovskite quantum dot light-emitting diodes (PeLEDs). Their electroluminescent performance was significantly improved, with their external quantum efficiency increasing to 12.05% and their turn-on voltage reduced to 2.5 V. These QLEDs exhibit excellent optoelectronic characteristics and provide new insights into surface ligand design criteria for tuning the surface chemistry of PeQDs. This optimisation is essential for improving the efficiency of QLEDs and other optoelectronic devices.