Lead-free double perovskites Cs₂InCuCl₆ and (CH₃NH₃)₂InCuCl₆: electronic, optical, and electrical properties

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Lead-containing metal halide perovskites are widely studied for solar cells but raise environmental concerns.
• Developing lead-free alternatives with comparable or superior optoelectronic properties is crucial for sustainable energy technologies.

Purpose of the Study:

• To investigate indium-based inorganic (Cs₂InMX₆) and organic-inorganic hybrid (MA₂InCuCl₆) double perovskites as potential lead-free solar cell materials.
• To evaluate their electronic and optical properties using computational methods.

Main Methods:

• Density functional theory (DFT) calculations using Kohn-Sham formalism.
• Exploration of various indium-based double perovskite compositions (M = Cu, Ag, Au; X = Cl, Br, I).
• Band gap, absorption coefficient, and charge carrier mobility calculations.

Main Results:

• Cs₂InCuCl₆ and MA₂InCuCl₆ identified as promising candidates.
• Cs₂InCuCl₆ exhibits a direct band gap (1.05–1.73 eV) and high absorption coefficient, exceeding c-Si and CdTe.
• MA₂InCuCl₆ has an indirect band gap (1.31–2.09 eV) with a higher absorption coefficient than c-Si and CdTe.
• Intrinsic charge carrier mobilities of Cs₂InCuCl₆ are comparable to MAPbI₃.

Conclusions:

• Cs₂InCuCl₆ and MA₂InCuCl₆ are promising lead-free semiconductors for photovoltaic and optoelectronic applications.
• Calculated band edge positions provide guidance for heterojunction design.
• Further experimental validation is warranted to confirm their potential.