Lead-Free Small-Bandgap Cs₂CuSbCl₆ Double Perovskite Nanocrystals

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Lead-free halide double perovskites (DPs) are gaining attention for their stability, nontoxicity, and favorable photophysical properties.
• Developing novel DPs with tunable bandgaps is crucial for advanced optoelectronic applications.

Purpose of the Study:

• To synthesize and characterize a new lead-free double perovskite Cs₂CuSbCl₆ nanocrystal (NC) material.
• To investigate the photophysical properties and stability of the synthesized Cs₂CuSbCl₆ NCs.
• To evaluate the potential of Cs₂CuSbCl₆ NCs for photovoltaic applications.

Main Methods:

• Synthesis of Cs₂CuSbCl₆ double perovskite nanocrystals (NCs).
• Experimental characterization of bandgap using spectroscopy.
• Density functional theory (DFT) calculations for electronic structure validation.
• Femtosecond and nanosecond transient absorption (TA) spectroscopy to study photophysical properties.
• Assessment of air stability.

Main Results:

• A new Cs₂CuSbCl₆ DP NC with a small bandgap of 1.66 eV was successfully synthesized, the smallest reported for 3D lead-free DP NCs.
• DFT calculations confirmed an indirect bandgap of 1.70 eV, aligning well with experimental findings.
• Photophysical properties were elucidated using femtosecond and nanosecond transient absorption techniques.
• The Cs₂CuSbCl₆ NCs demonstrated good stability when exposed to air.

Conclusions:

• The synthesized Cs₂CuSbCl₆ DP NCs possess a record-small bandgap and favorable photophysical characteristics.
• These NCs exhibit promising stability, making them suitable for practical applications.
• Cs₂CuSbCl₆ NCs represent a significant advancement for lead-free light-absorbing materials in photovoltaics.