Comparison of Ag(In,Ga)Se₂/Mo and Cu(In,Ga)Se₂/Mo Interfaces in Solar Cells

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Device Physics

Background:

• Molybdenum (Mo) is a common back contact material in thin-film solar cells.
• Understanding the interface properties between absorber layers and back contacts is crucial for device performance.

Purpose of the Study:

• Characterize the structural and electrical properties of Ag(In,Ga)Se2 (AIGS)/Mo and Cu(In,Ga)Se2 (CIGS)/Mo interfaces.
• Investigate the role of interfacial layers in determining contact type (ohmic vs. Schottky).

Main Methods:

• X-ray diffraction (XRD) and energy-dispersive X-ray spectrometry (EDX) for structural and compositional analysis.
• Electrical characterization to determine contact properties (barrier height, nonideality factor, series resistance).

Main Results:

• A MoSe2 layer (10-15 nm thick) with hexagonal structure was observed at the CIGS/Mo interface, but not at the AIGS/Mo interface.
• The CIGS/Mo interface with MoSe2 exhibited an ohmic contact.
• The AIGS/Mo interface without MoSe2 showed a Schottky contact with a barrier height of 0.8 ± 0.02 eV.

Conclusions:

• The formation of a MoSe2 interfacial layer significantly influences the electrical contact properties.
• The absence of MoSe2 at the AIGS/Mo interface leads to a rectifying Schottky contact, impacting device performance.