High-speed doctor-blading boosts organic solar cell efficiency

In a recent advancement, researchers have developed a high-speed doctor-blading technique that enhances the efficiency of organic solar cells (OSCs) while using eco-friendly, non-halogenated solvents.

This innovative method not only addresses the environmental and scalability challenges of traditional solvents, such as chloroform, but also achieves impressive power conversion efficiencies (PCEs) of 18.20% and 17.36% with green solvents like o-xylene and toluene, respectively. With a module efficiency of 16.07%, this breakthrough sets the stage for more sustainable, large-scale manufacturing of OSCs.

Organic solar cells (OSCs) are hailed for their lightweight, flexible design and their potential for low-cost, roll-to-roll production. However, the widespread use of halogenated solvents, including chloroform, has raised concerns due to their environmental and health hazards.

These solvents also limit scalability, as they require high concentrations and narrow processing windows that complicate large-scale production. While non-halogenated green solvents have been considered a safer alternative, their lower solubility and suboptimal film morphology have historically hindered device performance. This has created a significant need for new fabrication methods that can optimize green solvents without sacrificing efficiency.

Published in the Journal of Central South University, a research team introduced a high-speed doctor-blading method that overcomes these challenges. The technique reduces the necessary solution concentration for OSCs, enabling the use of environmentally friendly solvents like o-xylene and toluene without compromising efficiency. The team demonstrated a remarkable module efficiency of 16.07% using o-xylene, showcasing the potential for greener, scalable OSC production.

By employing the high-speed doctor-blading technique at 70 mm/s, the researchers reduced the solution concentration to just 8.8 mg/mL—significantly lower than the 15.4 mg/mL required for traditional spin coating methods. This allowed the use of non-halogenated solvents, which are more environmentally sustainable.

The results were striking, with the o-xylene-processed devices achieving a PCE of 18.20%, surpassing the 17.36% efficiency of toluene-processed devices. The longer liquid-to-solid transition time of 6 seconds with o-xylene, compared to just 1.7 seconds with toluene, played a critical role in enhancing film crystallinity, reducing defects, and boosting carrier mobility.

Morphological analysis confirmed that o-xylene-processed films exhibited superior molecular packing and crystallinity, further contributing to the higher efficiency. Additionally, the scalability of the technique was demonstrated with the successful achievement of a module efficiency of 16.07%.

Dr. Jun-liang Yang, the corresponding author of the study, emphasized the significance of the team’s findings. “This study represents a significant leap forward in the field of organic photovoltaics,” he said. “By developing a high-speed doctor-blading technique that works with non-halogenated solvents, we have not only improved the efficiency of organic solar cells but also made them more environmentally sustainable and scalable for industrial applications.”

The development of this high-speed doctor-blading technique offers a promising solution for the mass production of organic solar cells using green solvents, addressing both environmental concerns and scalability challenges. This innovation has the potential to significantly reduce the carbon footprint of solar cell manufacturing while maintaining high efficiency.

With module efficiencies exceeding 16% using non-halogenated solvents, this technology holds great promise for a variety of commercial applications, including flexible, lightweight solar panels for portable electronics, building-integrated photovoltaics, and large-scale solar farms. This research highlights the role of green solvents in advancing renewable energy technologies and driving a more sustainable energy future.

Provided by
Central South University