Stable Hexylphosphonate-Capped Blue-Emitting Quantum-Confined CsPbBr₃ Nanoplatelets

Area of Science:

• Materials Science
• Nanotechnology
• Quantum Dot Technology

Background:

• Quantum-confined cesium lead bromide (CsPbBr3) nanoplatelets (NPLs) show potential for blue light-emitting diodes (LEDs).
• Coalescence of CsPbBr3 NPLs in solution and films hinders their application, especially under device operating conditions.

Purpose of the Study:

• To investigate the use of hexyl-phosphonate ligands to suppress coalescence in CsPbBr3 NPLs.
• To enhance the stability and performance of blue-emitting CsPbBr3 NPLs for LED applications.

Main Methods:

• A heat-up colloidal approach was used to synthesize CsPbBr3 NPLs with hexyl-phosphonate ligands.
• Characterization included photoluminescence quantum yield measurements and solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy (13C, 133Cs, 31P).
• Density functional theory (DFT) calculations were performed to understand ligand binding affinities.

Main Results:

• Hexyl-phosphonate ligands significantly suppressed NPL coalescence compared to oleyammonium ligands.
• Phosphonate-passivated NPL thin films achieved photoluminescence quantum yields of ~40% at 450 nm with excellent ambient and thermal stability.
• Color purity was maintained under high photoexcitation densities (~3.5 A/cm2), and NMR confirmed phosphonate presence on the NPL surface.

Conclusions:

• Hexyl-phosphonate ligands offer superior surface passivation for CsPbBr3 NPLs, preventing coalescence and improving stability.
• The stronger binding affinity of phosphonate ligands, as suggested by DFT, is key to enhanced NPL performance.
• These findings pave the way for more stable and efficient blue LEDs based on CsPbBr3 NPLs.