[Study on back contact layer of CdTe solar cell by XPS]

Area of Science:

• Materials Science
• Thin Film Deposition
• Semiconductor Physics

Context:

• Zinc telluride (ZnTe) and copper-doped ZnTe (ZnTe:Cu) polycrystalline films are crucial for photovoltaic applications.
• Controlling elemental distribution, particularly copper diffusion, is vital for optimizing film properties and device performance.
• Previous methods struggled with effective copper diffusion management in ZnTe films.

Purpose:

• To investigate the structural and compositional properties of ZnTe and ZnTe:Cu films fabricated by co-evaporation.
• To understand the influence of deposition parameters on copper distribution within ZnTe films.
• To develop a novel deposition strategy to mitigate copper diffusion and enhance solar cell efficiency.

Summary:

• Films were fabricated using co-evaporation at room temperature, with structural and elemental analysis performed using X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS).
• XRD confirmed stable phase structure across different substrate temperatures, while XPS revealed deposition rate-dependent compositional variations and a characteristic copper distribution profile over sputtering time.
• A new method involving sequential deposition—first ZnTe at 70°C, then ZnTe:Cu at room temperature—was devised to effectively prevent copper diffusion.

Impact:

• The developed deposition technique successfully prevents copper atom diffusion in ZnTe films.
• This advancement leads to improved efficiency in cadmium telluride (CdTe) solar cells.
• Provides a scalable method for fabricating high-performance ZnTe-based thin films for optoelectronic devices.