KCN Chemical Etch for Interface Engineering in Cu2ZnSnSe4 Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Thin Film Technology

Background:

• Secondary phase removal is crucial for enhancing kesterite (Cu2ZnSn(S,Se)4 or CZTSSe) thin film solar cell performance.
• Existing chemical etching methods for related materials are adapted to address CZTSSe surface challenges.

Purpose of the Study:

• To investigate the impact of KCN/KOH chemical etching on CZTSSe absorbers with varying compositions.
• To analyze the resulting electrical behavior and identify the underlying mechanisms affecting solar cell performance.

Main Methods:

• Application of a KCN/KOH chemical etching process to CZTSSe absorbers.
• Electrical characterization of CZTSSe/CdS solar cells before and after etching.
• Analysis of surface composition changes and their correlation with device performance.

Main Results:

• Short etching (30s) improved fill factor (FF) in CZTSSe with initial electrical distortions by removing secondary phases like CuxSe and SnSex.
• Extended etching degraded FF in all Cu-poor CZTSSe samples due to preferential etching of Se, Sn, and Zn by KOH.
• Etching induced a Cu-rich shell at the absorber/buffer interface, increasing recombination and degrading FF.

Conclusions:

• KCN/KOH etching offers a method to improve CZTSSe solar cells by removing detrimental surface phases.
• Optimizing etching time is critical to balance secondary phase removal and avoid performance degradation caused by preferential etching and interface modification.