Understanding Optical Properties and Electronic Structures of High-Entropy Alloyed Perovskite Nanocrystals

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• High-entropy alloying (HEA) is a strategy to tune nanomaterial properties.
• Its application in luminescent semiconductor nanocrystals (NCs) is limited by a poor understanding of electronic and photophysical effects.
• Metal halide perovskite NCs offer defect tolerance, making them suitable for HEA.

Purpose of the Study:

• To synthesize and characterize high-entropy halide perovskite (HEP) NCs.
• To investigate the electronic structure modifications induced by HEA.
• To correlate these changes with photophysical properties and photostability.

Main Methods:

• Synthesis of multi-element B-site substituted perovskite NCs (Pb, Sr, Ca, Cd, Mg).
• Characterization using high-resolution transmission electron microscopy, transient photoluminescence and absorption spectroscopy, and X-ray photoemission spectroscopy.
• Theoretical analysis using density functional theory simulations.

Main Results:

• HEA reduces band dispersion and broadens the conduction band in HEP NCs.
• Excitonic features are diminished due to the formation of near band-edge shallow states.
• These shallow states promote rapid radiative recombination and enhance photostability.
• Significant reduction of lead content (up to 70%) was achieved.

Conclusions:

• HEA effectively engineers the electronic structure of perovskite NCs.
• The induced shallow states are key to improved radiative recombination and photostability.
• HEA is a versatile strategy for band structure engineering and stabilization of perovskite NCs with reduced lead.