Role of CdTe Interface Structure on CdS/CdTe Photovoltaic Device Performance

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Cadmium Telluride (CdTe) solar cells are a key photovoltaic technology.
• The CdS/CdTe heterojunction is critical for device performance.
• Controlling crystal structure at interfaces is essential for optimizing solar cells.

Purpose of the Study:

• To investigate the role of Glancing Angle Deposition (GLAD) CdTe interlayers in tailoring the CdS/CdTe heterojunction.
• To optimize photovoltaic (PV) device performance by controlling interfacial properties.
• To evaluate the impact of GLAD CdTe interlayer thickness and deposition conditions on solar cell efficiency.

Main Methods:

• Preparation of GLAD CdTe films at various oblique deposition angles (Φ) and temperatures (room temperature [RT] and 250 °C [HT]).
• Fabrication of CdS/CdTe heterojunctions using GLAD CdTe as interlayers.
• Characterization of crystal structure (cubic, hexagonal, mixed) of GLAD CdTe films.
• Evaluation of photovoltaic device performance, including open-circuit voltage and fill-factor.

Main Results:

• GLAD CdTe films exhibit different crystal structures (cubic, hexagonal, mixed) based on deposition angle and temperature.
• A Φ = 80° RT GLAD CdTe interlayer, having a hexagonal structure, aligns with the hexagonal CdS layer, reducing lattice mismatch.
• Solar cells with a 250 nm thick Φ = 80° RT GLAD CdTe interlayer showed a significant improvement: 0.53 V increase in open-circuit voltage and fill-factor product, and a 0.73% absolute efficiency increase compared to baseline devices.

Conclusions:

• GLAD CdTe interlayers can effectively tailor the CdS/CdTe heterojunction by controlling crystal structure and reducing lattice mismatch.
• Optimized GLAD CdTe interlayers, particularly hexagonal ones, significantly enhance photovoltaic device performance.
• This interfacial engineering approach offers a promising route for improving CdTe solar cell efficiency.