Halogen-Driven Tunability in Cubic KZnX₃ (X = F-I) Halide Perovskites: A First-Principles Study

Area of Science:

• Materials Science
• Solid State Physics
• Computational Chemistry

Background:

• Cubic KZnX3 perovskites are promising materials for optoelectronic applications.
• Understanding their fundamental properties is crucial for device development.

Purpose of the Study:

• To systematically investigate the structural, mechanical, electronic, and optical properties of cubic KZnX3 (X = F, Cl, Br, I) perovskites.
• To explore the effect of halogen substitution on these properties.

Main Methods:

• Density Functional Theory (DFT) calculations using the Quantum Espresso framework.
• Structural optimization, stability analyses, elastic constant calculations, electronic structure calculations (HSE06), and optical property calculations.

Main Results:

• All KZnX3 compounds are thermodynamically, mechanically, and dynamically stable in the cubic Pm-3m phase.
• Materials exhibit anisotropic and ductile behavior with decreasing Debye temperatures from KZnF3 to KZnI3.
• Tunable indirect bandgaps decrease from 4.24 eV (KZnF3) to 0.86 eV (KZnI3), indicating suitability for optoelectronics.
• Increased polarizability, absorption, refractive index, and plasmonic response with heavier halogens.

Conclusions:

• Halogen substitution in KZnX3 perovskites is an effective strategy for tuning their electronic and optical characteristics.
• The tunable semiconducting properties and enhanced optical responses highlight their potential for photovoltaic and optoelectronic devices.