Effect of Al₂O₃ Dot Patterning on CZTSSe Solar Cell Characteristics

Area of Science:

• Materials Science
• Photovoltaics
• Thin Film Technology

Background:

• Copper zinc tin sulfide selenide (CZTSSe) is a promising kesterite semiconductor for thin-film solar cells.
• Optimizing the rear contact structure is crucial for enhancing CZTSSe solar cell performance and stability.
• Understanding the interaction between the electrode material and the CZTSSe layer is key to device fabrication.

Purpose of the Study:

• To investigate the impact of patterned aluminum oxide (Al2O3) layers on molybdenum (Mo) electrodes on copper zinc tin sulfide selenide (CZTSSe) growth.
• To analyze the effect of varying Al2O3 coverage on the rear contact structure of CZTSSe solar cells.
• To determine the relationship between the patterned rear contact and the overall solar cell efficiency.

Main Methods:

• Fabrication of CZTSSe solar cells with a 5-nm Al2O3 layer patterned as dots on the Mo electrode.
• Varied Al2O3 coverage ratios (56%, 75%, 84%) to create local rear contacts.
• Characterization of CZTSSe growth, film morphology, and solar cell device performance.

Main Results:

• Al2O3 patterning effectively suppressed MoSSe formation under the coated areas.
• A self-alignment phenomenon was observed in the back-contact region.
• CZTSSe formation was favored in exposed Mo areas, but voids formed near Al2O3-coated regions.
• Increased Al2O3 coverage led to a decrease in solar cell efficiency.

Conclusions:

• The efficiency of CZTSSe solar cells is inversely related to the area of Al2O3 passivation.
• Optimization of the Mo-exposed pattern and controlled sodium (Na) supply are critical for developing efficient self-aligned CZTSSe absorbers.
• Further research is needed to balance passivation effects and conductive pathways for improved device performance.