Enhanced visible light absorption for lead-free double perovskite Cs₂AgSbBr₆

Area of Science:

• Materials Science
• Solid-State Chemistry
• Photovoltaics

Background:

• Growing demand for lead-free photovoltaic materials.
• Exploration of double perovskite structures for optoelectronic applications.

Purpose of the Study:

• Synthesize and characterize a new lead-free double perovskite, Cs2AgSbBr6.
• Investigate its structural, optical, and electronic properties for photovoltaic potential.

Main Methods:

• Single crystal X-ray diffraction for structural determination.
• X-ray photoelectron spectroscopy (XPS) for chemical state analysis.
• UV-Visible spectroscopy and Density Functional Theory (DFT) calculations for optical and electronic properties.

Main Results:

• Successfully synthesized Cs2AgSbBr6 with an indirect optical bandgap of 1.64 eV.
• Determined crystal structure (space group Fm3[combining macron]m, a = 11.1583(7) Å).
• Observed a color change from black to brown upon heating, linked to Sb3+-Sb5+ charge transfer, without loss of symmetry or crystallinity.

Conclusions:

• Cs2AgSbBr6 is a promising lead-free material for photovoltaic applications.
• The observed color change is attributed to intervalence charge transfer.
• Further research into its electronic structure and device performance is warranted.