Suppressing Deep-Level Trap Toward Over 13% Efficient Solution-Processed Kesterite Solar Cell

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Copper Zinc Tin Sulfide Selenide (CZTSSe) is a key material for thin-film solar cells.
• Defects and high defect concentrations limit CZTSSe solar cell efficiency.
• High-temperature selenization processes influence defect formation in CZTSSe.

Purpose of the Study:

• To optimize copper zinc tin sulfide (CZTS) precursor films using a NaOH-Se intermediate layer.
• To improve grain growth and reduce defects during CZTSSe selenization.
• To enhance the performance of CZTSSe thin-film solar cells through back interface engineering.

Main Methods:

• Introduction of a NaOH-Se intermediate layer at the back interface of CZTS precursor films.
• High-temperature selenization process to form CZTSSe absorber layers.
• Characterization of film morphology, defect levels, and device performance.

Main Results:

• The NaOH-Se intermediate layer optimized Se and alkali metal content, promoting grain growth.
• Morphological issues like non-uniform grains, voids, and poor back contact were addressed.
• Deep-level defects were suppressed, enhancing carrier transport.
• CZTSSe devices exhibited a 13.3% improvement in fill factor, open-circuit voltage, and efficiency.

Conclusions:

• Back interface engineering with a NaOH-Se layer is effective for fabricating high-quality CZTSSe absorber layers.
• This approach significantly improves the performance of kesterite solar cells.
• Understanding the role of intermediate layers is crucial for advancing solar cell technology.