Regulating Donor Aggregation via Alkyl Side-Chain Engineering for Green-Solvent Processed Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Sustainable Chemistry

Background:

• Scalable fabrication of organic solar cells (OSCs) requires replacing toxic halogenated solvents with eco-friendly alternatives.
• Processing OSCs with non-halogenated solvents often results in poor morphology and limited device performance due to uncontrolled donor aggregation.

Purpose of the Study:

• To develop a molecular design strategy for efficient morphology control in OSCs using green processing conditions.
• To enable high-performance OSCs manufactured with environmentally benign solvents.

Main Methods:

• Synthesized a series of terpolymers (D18-Cl-xHD) by random copolymerization of D18-Cl with DTBT-HD units, introducing long even-numbered alkyl chains.
• Fine-tuned terpolymer solubility and aggregation behavior through rational side-chain engineering.
• Processed the optimized terpolymer (D18-Cl-10HD) from o-xylene and characterized its performance and morphology.

Main Results:

• The optimized terpolymer, D18-Cl-10HD, achieved a power conversion efficiency of 18.1% when processed from o-xylene, a >60% improvement over the D18-Cl benchmark.
• Morphological analysis showed D18-Cl-10HD forms a well-ordered bicontinuous network with enhanced molecular packing and domain purity.
• These morphological improvements facilitate efficient exciton dissociation and charge transport.

Conclusions:

• The study presents a broadly applicable strategy for designing green-solvent-compatible materials for OSCs.
• Established a deeper mechanistic understanding of side-chain-regulated phase behavior in organic semiconductors.
• Bridged the gap between high efficiency and sustainable manufacturing in the field of organic solar cells.