Selenization Reaction Driving Force Regulation for High-Quality Absorber Enabling Li&Na Co-Doped Flexible CZTSSe...

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• High-quality kesterite Cu2ZnSn(S,Se)4 (CZTSSe) absorbers are crucial for efficient flexible solar cells.
• Developing advanced fabrication methods is essential for improving CZTSSe absorber quality and device performance.

Purpose of the Study:

• To develop a tailored selenization process for enhancing CZTSSe absorber quality in flexible solar cells.
• To investigate the impact of this process on device performance, including fill factor, carrier recombination, and power conversion efficiency.

Main Methods:

• A novel selenization process was developed, utilizing the bendability of molybdenum (Mo) foil substrates.
• This method aimed to enhance the driving force of the selenization reaction for improved CZTSSe absorber formation.
• Characterization of CZTSSe absorbers and fabricated solar cell devices was performed.

Main Results:

• The tailored selenization process resulted in denser CZTSSe absorbers with significantly improved crystallinity.
• The quality of the CZTSSe/CdS heterojunction improved, leading to an increase in the fill factor (FF) from 64.76% to 70.62%.
• Carrier recombination at the CZTSSe/CdS interface was suppressed, and back-contact barrier height decreased by 13.16%, enhancing charge transport.
• The optimized flexible CZTSSe solar cell achieved a champion power conversion efficiency (PCE) of 12.42% and an open-circuit voltage (VOC) of 0.55 V.
• Improved performance uniformity was observed, with a 1.22 cm2 flexible device reaching 9.59% PCE.

Conclusions:

• The developed tailored selenization process is a novel and effective strategy for improving the quality and performance of flexible CZTSSe solar cells.
• This approach offers a promising pathway for advancing the efficiency and uniformity of next-generation flexible photovoltaic devices.