Strain-engineered Si-doped Cs₃Bi₂I₉ perovskite for high-performance MIM capacitors: a DFT study.

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Cesium bismuth iodide (Cs3Bi2I9) perovskites are explored for electronic applications.
• Understanding their electronic and electromechanical properties is crucial for device development.
• Lead-free perovskites are sought after to replace toxic lead-based materials.

Purpose of the Study:

• To investigate the energy storage potential of strain-engineered, silicon (Si)-doped Cs3Bi2I9 perovskites.
• To evaluate key electronic and electromechanical parameters, including band gap, polarization, and leakage suppression.
• To establish a lead-free perovskite platform for next-generation metal-insulator-metal (MIM) capacitors.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• Electronic and electromechanical parameters were computed for intrinsic and strained systems.
• Born effective charge (BEC) analysis was used to understand local polarization.

Main Results:

• Undoped Cs3Bi2I9 has a wide band gap (3.3 eV) and low polarization, suitable for insulation.
• 0.25 mol% Si doping narrows the band gap and enhances dielectric constant and capacitance.
• Optimized doping (0.25% Si) and 0.10% strain yield high polarization (~1 C m-2), strong piezoelectricity, and reduced leakage.
• Higher doping (0.50% Si) under strain leads to excessive polarization and increased leakage.

Conclusions:

• Si-doping and strain engineering synergistically enhance dielectric behavior and polarization in Cs3Bi2I9.
• This study demonstrates a novel, lead-free perovskite material for energy storage and flexible electronics.
• The findings establish Si-doped Cs3Bi2I9 as a promising candidate for high-performance MIM capacitors.