Electrostatic potentials at Cu(In,Ga)Se2 grain boundaries: experiment and simulations.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Grain boundaries (GBs) significantly influence material properties.
• The symmetry of grain boundaries affects their physical characteristics.
• Understanding electrostatic potentials at GBs is crucial for predicting material behavior.

Purpose of the Study:

• To investigate the electrostatic potential at a low-symmetry Σ9 grain boundary in CuGaSe2.
• To correlate the potential well characteristics with GB symmetry and atomic structure.
• To validate theoretical calculations with experimental observations.

Main Methods:

• Ab initio density functional theory (DFT) calculations.
• Multislice simulation techniques.
• Transmission electron microscopy (TEM) based electron holography.

Main Results:

• An electrostatic potential well of 0.8 V depth and 1.3 nm width was identified at the Σ9 GB.
• Potential well depth increases with decreasing grain boundary symmetry (Σ9 vs. Σ3 and random GBs).
• The potential well is attributed to a reduced atomic density at the grain boundary.

Conclusions:

• The study establishes a clear relationship between grain boundary symmetry and electrostatic potential.
• Theoretical and experimental results show quantitative agreement, validating the findings.
• This work provides fundamental insights into the nature of grain boundaries in CuGaSe2.