Characterization of Zn(O,S) Buffer Layers for Cu(In,Ga)Se2 Solar Cells

Area of Science:

• Materials Science
• Thin Film Deposition
• Semiconductor Physics

Background:

• Thin films are crucial components in various electronic devices, including solar cells.
• Optimizing buffer layers in solar cells is essential for enhancing device efficiency and stability.

Purpose of the Study:

• To investigate the deposition of zinc oxysulfide (Zn(O,S)) thin films using radio-frequency magnetron sputtering.
• To analyze the effects of oxygen concentration on film properties and their suitability as buffer layers for Cu(In,Ga)Se2 solar cells.

Main Methods:

• Radio-frequency magnetron sputtering of a ZnS target in an Ar/O2 atmosphere at room temperature.
• Optical emission spectroscopy (OES) to analyze plasma characteristics.
• X-ray diffraction (XRD) and scanning electron microscopy (SEM) for structural and morphological analysis.
• X-ray photoelectron spectroscopy (XPS) for elemental composition and chemical bonding analysis.

Main Results:

• Deposition rates decreased with increasing O2 concentration due to O- formation.
• Stable Zn(O,S) crystalline structure was observed up to 0.6% O2; instability occurred above 0.8% O2.
• XRD and SEM confirmed a Zn(O,S) crystal structure with partial O for S substitution and uniform, dense grains.
• XPS revealed uniform elemental composition and mixed crystal structure with Zn-O bonding.

Conclusions:

• Zn(O,S) thin films deposited by RF sputtering are suitable for application as buffer layers in Cu(In,Ga)Se2 solar cells.
• Optimizing oxygen concentration during deposition is critical for achieving stable and high-quality films.