Li-Doped Front Interface Engineering Enables Flexible Kesterite Solar Cell With 12.31% Efficiency and Module With...

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Flexible kesterite Cu2ZnSn(S, Se)4 (CZTSSe) solar cells face efficiency limitations due to open-circuit voltage deficit (Voc,def).
• This deficit is primarily caused by carrier recombination at the CZTSSe/CdS interface, stemming from numerous defects.

Purpose of the Study:

• To mitigate carrier recombination and improve the performance of flexible CZTSSe solar cells.
• To investigate the impact of lithium ion doping on the CZTSSe/CdS interface and overall device efficiency.

Main Methods:

• A modification strategy involving doping lithium ions at the front interface of CZTSSe absorbers.
• Fabrication of flexible CZTSSe solar cells and subsequent assembly into flexible solar modules using shingled technology.

Main Results:

• Lithium ion doping effectively inhibited secondary phases and defects in the CZTSSe absorber.
• A high-quality CZTSSe/CdS heterojunction was formed, decreasing interface defect states from 2.90 × 10^15 to 9.00 × 10^14 cm^-3.
• Achieved a power conversion efficiency of 12.31% for flexible CZTSSe solar cells (Voc = 0.555 V).
• Assembled flexible solar modules (4.56 cm^2) with 7.85% efficiency and Voc over 2 V.

Conclusions:

• Lithium ion doping is a viable strategy to reduce carrier recombination and enhance the performance of flexible kesterite solar cells.
• Shingled technology demonstrates potential for creating high-efficiency flexible solar modules.