A Redox-Active Ionic Liquid Surface Treatment for Healing CsPbBr₃ Nanocrystals

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Additive engineering is crucial for mitigating defects in lead halide perovskites.
• Ionic liquids (ILs) have shown efficacy in passivating halide vacancies in perovskite materials and nanocrystals.
• Existing IL treatments primarily address halide vacancies, leaving other defect types unaddressed.

Purpose of the Study:

• To introduce a novel phosphonium tribromide ionic liquid for treating CsPbBr3 nanocrystals.
• To investigate the capability of this IL to heal metallic lead surface defects via redox chemistry.
• To evaluate the impact of this redox-active IL treatment on photoluminescence quantum yield (PLQY).

Main Methods:

• Synthesis and application of a novel phosphonium tribromide ionic liquid.
• Treatment of CsPbBr3 nanocrystals with the developed IL.
• Characterization of treated nanocrystals, focusing on surface defect passivation and PLQY measurements.
• Comparison with treatments using non-redox-active bromide ILs.

Main Results:

• The novel phosphonium tribromide IL successfully heals metallic lead surface defects in CsPbBr3 nanocrystals.
• Redox chemistry mediated by the IL is responsible for the observed defect passivation.
• A significant increase in photoluminescence quantum yield (PLQY) was achieved, outperforming non-redox-active IL treatments.

Conclusions:

• Redox-active ionic liquids represent a new class of additives for advanced defect engineering in semiconductor nanocrystals.
• This work expands the scope of IL-mediated defect passivation beyond halide vacancies to include metallic surface defects.
• The findings pave the way for enhanced performance and stability in perovskite-based optoelectronic devices.