First-Principles Study of Antisite Defect Configurations in ZnGa2O4:Cr Persistent Phosphors

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Chromium-doped zinc gallate (ZnGa2O4:Cr) is a promising near-infrared persistent phosphor.
• Its luminescence mechanism is linked to intrinsic defects, particularly antisite defects and pairs.
• Applications include in vivo bioimaging and security features.

Purpose of the Study:

• To elucidate the role of defects and dopants in ZnGa2O4:Cr persistent luminescence.
• To investigate the interactions between chromium dopants and antisite defects.
• To understand the stability and formation mechanisms of these complex materials.

Main Methods:

• Density-functional theory (DFT) simulations using large periodic supercells.
• Calculation of formation energies, dopant energies, and defect energies.
• Analysis of structural distortions, Hirshfeld-I charges, and densities of states.

Main Results:

• DFT calculations confirm chromium substitution at the gallium site, introducing energy levels within the band gap.
• Antisite pairs (e.g., ZnGa) are energetically favored over isolated antisites due to charge compensation.
• Significant structural distortions occur around antisite defects, influenced by the ZnGa antisite and local Cr environment.
• The distance between antisite pairs is a critical factor for material stability.

Conclusions:

• Antisite pairs play a crucial role in the persistent luminescence of ZnGa2O4:Cr.
• Charge compensation and structural distortions around defects significantly impact material properties.
• Theoretical modeling provides insights into the complex defect physics governing the phosphor's performance.