A-site cation engineering in lead-free halide double perovskites A₂AgSbBr₆ (A = Na, K, Rb): a comprehensive...

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Lead-free halide double perovskites offer a stable and tunable alternative to lead-based materials.
• These materials are being explored for optoelectronic and photovoltaic applications.

Purpose of the Study:

• To investigate the structural, mechanical, electronic, optical, and bonding properties of A₂AgSbBr₆ (A = Na, K, Rb) double perovskites.
• To identify promising lead-free perovskite candidates for optoelectronic and photovoltaic applications.

Main Methods:

• First-principles calculations using Density Functional Theory (DFT) with the CASTEP code.
• Generalized Gradient Approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) functional for exchange-correlation.
• Structural optimization via BFGS minimization, ultrasoft pseudopotentials, and Monkhorst-Pack k-point sampling.

Main Results:

• All A₂AgSbBr₆ compounds exhibit cubic phase stability.
• Indirect semiconducting band gaps were observed, varying with the A-site ionic radius.
• Sb-Br bonds show strong covalent characteristics, and all compounds display ductile mechanical behavior.
• Strong light absorption and optical response in the visible to near-UV regions were found.
• K₂AgSbBr₆ demonstrated the most favorable electronic and optical properties.

Conclusions:

• A₂AgSbBr₆ double perovskites are stable and possess suitable electronic and optical properties for optoelectronics.
• K₂AgSbBr₆ is a particularly promising lead-free material for photovoltaic and optoelectronic device applications.