Regulating Hetero-Nucleation Enabling Over 14% Efficient Kesterite Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Developing high-quality kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) light-absorbing layers is crucial for advancing CZTSSe solar cell efficiency.
• Optimizing the high-temperature selenization reaction is key but complex, requiring better understanding of its mechanisms.

Purpose of the Study:

• To introduce a precursor microstructure-guided hetero-nucleation regulation strategy for fabricating high-quality CZTSSe absorbers.
• To improve the performance of CZTSSe solar cells through controlled selenization.

Main Methods:

• Suppressed alcoholysis of 2-methoxyethanol (MOE) and micelle generation using hydrogen chloride (HCl) as a proton additive in the precursor solution.
• Tailored modification of solution components to reduce volatile emissions during baking, resulting in a compact precursor microstructure.
• Utilized the reduced-roughness precursor surface to promote larger CZTSSe nuclei formation and accelerate Ostwald ripening.

Main Results:

• Achieved CZTSSe absorbers with enhanced crystallinity and reduced defects.
• Fabricated CZTSSe solar cells with an impressive 14.01% active-area power conversion efficiency.
• Demonstrated the significant influence of precursor microstructure on the selenization reaction.

Conclusions:

• The developed strategy effectively controls the selenization process by manipulating precursor microstructure.
• This approach provides a viable route for producing high-quality kesterite CZTSSe films for efficient solar cells.
• The findings offer fundamental insights into the relationship between precursor characteristics and film formation in CZTSSe solar cells.