An ITO-Free Kesterite Solar Cell

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Kesterite Cu2ZnSn(S, Se)4 (CZTSSe) thin film solar cells show promise but are limited by low open-circuit voltage (VOC) due to interface recombination.
• High-density interface states between absorber and buffer/window layers hinder photogenerated carrier collection and reduce overall efficiency.

Purpose of the Study:

• To address the efficiency limitations of CZTSSe solar cells by proposing a new window structure.
• To improve the optoelectronic properties and junction quality of CZTSSe devices through a low-damage processing method.

Main Methods:

• A novel ZnO/AgNW/ZnO/AgNW (ZAZA) window structure was designed and implemented.
• The ZAZA structure was integrated into CZTSSe solar cells as an alternative to traditional indium tin oxide (ITO).
• Device performance was evaluated based on open-circuit voltage (VOC), built-in voltage (Vbi), carrier collection, and overall conversion efficiency.

Main Results:

• The ZAZA-based CZTSSe solar cells demonstrated enhanced VOC attributed to higher built-in voltage (Vbi) and reduced interface recombination.
• Improved carrier collection was observed due to shortened collection paths and more uniform carrier lifetime distribution.
• The fabricated devices achieved over 10% sunlight-to-electricity conversion efficiency without anti-reflective coating, marking the first ITO-free CZTSSe cells with this performance.

Conclusions:

• The proposed ZAZA window structure offers a viable, low-damage alternative to ITO for CZTSSe solar cells.
• This advancement significantly improves device performance by mitigating interface recombination and enhancing carrier dynamics.
• The development paves the way for more efficient and cost-effective ITO-free kesterite thin film solar cells.