The surface chemistry of ionic liquid-treated CsPbBr3 quantum dots

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Lead halide perovskite solar cells show rapidly increasing power conversion efficiencies.
• Ionic liquids (ILs) are used as additives and interface modifiers, boosting cell performance.
• Atomistic understanding of IL-perovskite surface interactions is limited due to film characteristics.

Purpose of the Study:

• To investigate the coordinative surface interactions between phosphonium-based ionic liquids (ILs) and CsPbBr3 perovskite.
• To elucidate the effect of ILs on perovskite quantum dots (QDs) at an atomistic level.
• To determine optimal IL compositions for enhancing perovskite solar cell performance.

Main Methods:

• Utilized CsPbBr3 quantum dots (QDs) as model systems for perovskite surfaces.
• Performed ligand exchange on QD surfaces using phosphonium-based ILs (cation and anion).
• Analyzed changes in photoluminescent quantum yield (PLQY) and characterized QD structure, shape, and size.

Main Results:

• Exchanged native ligands with IL components, resulting in a threefold increase in QD photoluminescent quantum yield.
• Observed no changes in CsPbBr3 QD structure, shape, or size at equimolar IL additions, indicating surface-level interaction.
• Found that increased IL concentrations led to detrimental phase changes and reduced PLQY.

Conclusions:

• Demonstrated a surface-level coordinative interaction between phosphonium-based ILs and CsPbBr3 perovskite QDs.
• Established that specific IL cation-anion pairings can significantly enhance perovskite photoluminescence.
• Provided insights for selecting beneficial ILs to improve perovskite solar cell efficiency and stability.