Zn_1-GeO Passivating Interlayers for BaSi₂ Thin-Film Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Barium disilicide (BaSi2) is a promising material for next-generation thin-film solar cells (TFSCs).
• High-efficiency TFSCs require suitable interlayers for optimal performance.
• No interlayer had been previously studied for BaSi2.

Purpose of the Study:

• To investigate amorphous Zn1-xGexOy films as interlayers for BaSi2.
• To determine the effect of substrate temperature on Zn1-xGexOy film properties.
• To evaluate the heterointerface and surface passivation effects of Zn1-xGexOy on BaSi2.

Main Methods:

• Sputtering deposition of amorphous Zn1-xGexOy films on BaSi2.
• Analysis of Zn/Ge atomic ratio and optical band gap dependence on substrate temperature.
• Photoresponsivity measurements to assess performance.
• X-ray photoelectron spectroscopy (XPS) to analyze surface chemistry.

Main Results:

• A suitable i-Zn1-xGexOy/BaSi2 heterointerface with spike-type conduction band offset was achieved at 50 °C.
• Zn1-xGexOy demonstrated excellent surface passivation for BaSi2.
• A 2 nm thick Zn1-xGexOy interlayer yielded a photoresponsivity of 0.9 A/W for a 500 nm BaSi2 layer at 780 nm.
• Short-wavelength photoresponsivity significantly improved compared to amorphous Si interlayers.
• XPS confirmed suppression of BaSi2 oxidation and reduced carrier recombination.

Conclusions:

• Amorphous Zn1-xGexOy films are effective interlayers for BaSi2 TFSCs.
• The developed interlayer provides suitable band alignment for carrier transport.
• This study presents the first demonstration of passivation interlayers for BaSi2 with improved performance.