A Polycrystalline Polymer Donor as Pre-Aggregate toward Ordered Molecular Aggregation for 19.3% Efficiency Binary...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic semiconductors exhibit limited structural order in solid films, hindering charge transport and increasing recombination in photovoltaic devices.
• Achieving high efficiency in organic solar cells requires optimized molecular packing and morphology in the active layer.

Purpose of the Study:

• To develop a "polycrystal-induced aggregation" strategy to improve molecular ordering in PM6:L8-BO organic solar cells.
• To enhance the power conversion efficiency (PCE) of organic solar cells with varying photoactive layer thicknesses.

Main Methods:

• Incubation of PM6 polycrystals via vapor diffusion.
• Preparation of PM6 pre-aggregates (PM6-PA) by redissolving PM6 polycrystals in chloroform.
• Incorporation of PM6-PA into conventional PM6:L8-BO blend solutions for solution casting.

Main Results:

• The addition of PM6-PA prolonged molecular organization and enhanced the aggregation of both PM6 and L8-BO components.
• Organic solar cells with a 100 nm-thick active layer achieved PCEs of 19.3% (up from 18.0%).
• Organic solar cells with a 300 nm-thick active layer achieved PCEs of 17.2% (up from 16.2%).

Conclusions:

• The "polycrystal-induced aggregation" strategy effectively improves molecular ordering in organic semiconductor films.
• This method leads to significant enhancements in organic solar cell performance, particularly for thicker active layers.
• The approach offers a viable route to higher efficiency organic photovoltaic devices.