New Method for Preparing ZnO Layer for Efficient and Stable Organic Solar Cells.

Area of Science:

• Materials Science
• Renewable Energy

Background:

• Zinc oxide (ZnO) is a key material in organic solar cells (OSCs) due to its optoelectronic properties and ease of preparation.
• Residual amine in ZnO can react with non-fullerene acceptors, negatively impacting OSC performance and stability.

Purpose of the Study:

• To develop a simple, economical, and effective method for removing residual amine from ZnO without compromising its structure.
• To enhance the performance and long-term stability of organic solar cells by optimizing the ZnO cathode interface layer.

Main Methods:

• Boric acid (BA) was chosen as an amine-removing agent due to its appropriate acidity and high water solubility.
• ZnO films were treated by rinsing with BA solution to remove residual amine.
• The work function, electron extraction, and stability of the cathode interface layer were analyzed.
• Single-junction and tandem OSCs were fabricated using BA-treated ZnO and characterized for power conversion efficiency (PCE) and stability.

Main Results:

• The BA treatment effectively removed residual amine from ZnO, optimizing the cathode interface layer.
• Treated ZnO improved electron extraction and enhanced the stability of the cathode interface.
• Single-junction OSCs achieved PCEs of 18.40% and 17.42% for 0.04 cm² and 1.00 cm² devices, respectively.
• Tandem OSCs utilizing BA-treated ZnO demonstrated a PCE of 19.56%.

Conclusions:

• The BA treatment is a reliable and effective method for improving ZnO-based organic solar cells.
• This approach significantly enhances both the power conversion efficiency and operational stability of OSCs.
• The developed method offers a practical solution for overcoming a key challenge in non-fullerene acceptor-based OSCs.