Design Principles for Trap-Free CsPbX₃ Nanocrystals: Enumerating and Eliminating Surface Halide Vacancies with Softer...

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Physics

Background:

• Cesium lead halide perovskites (CsPbX₃) are promising optoelectronic materials.
• Surface defects, particularly halide vacancies, significantly hinder their luminescence efficiency.
• Understanding and mitigating these surface traps is crucial for device applications.

Purpose of the Study:

• To elucidate the general surface passivation mechanism for CsPbX₃ nanocrystals.
• To identify the primary source of charge trapping at the nanocrystal surface.
• To develop a systematic approach for achieving highly luminescent CsPbX₃ materials.

Main Methods:

• Combined experimental (spectroscopic methods, ¹H NMR) and theoretical (ab initio calculations) studies.
• Identification and quantification of surface halide vacancies.
• Investigation of ligand-based passivation strategies targeting under-coordinated lead atoms.

Main Results:

• Surface halide vacancies are confirmed as the dominant charge trapping sites.
• A quantitative correlation between surface traps and luminescence quenching is established.
• Passivation with specific anionic ligands leads to near-unity absolute quantum yields and monoexponential luminescence decay.

Conclusions:

• A general surface passivation mechanism for CsPbX₃ nanocrystals is presented.
• Anionic ligands targeting under-coordinated lead atoms effectively passivate surface traps.
• This framework enables the rational design of highly luminescent CsPbX₃ materials with tailored properties.