"Twisted" Terpolymer Donor Enabling High-Performance Intrinsically Stretchable Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Intrinsically stretchable organic solar cells (is-OSCs) are promising for wearable power generation.
• Current high-efficiency organic solar cells use rigid backbones, limiting stretchability and creating a performance-mechanical trade-off.

Purpose of the Study:

• To develop ductile terpolymers that enhance both photovoltaic performance and mechanical robustness in is-OSCs.
• To investigate the impact of incorporating 3-butyloctyl-thiophene (ThBO) units into PM6 backbones on material properties and device performance.

Main Methods:

• Synthesized a series of PM-BOX% terpolymers with varying amounts of ThBO units (X = 5, 10, 20).
• Incorporated ThBO units into the PM6 backbone to induce backbone twisting and increase disordered content.
• Fabricated and characterized is-OSC devices using the developed terpolymers and a BTP-eC9 acceptor.

Main Results:

• The PM-BO10%:BTP-eC9 devices achieved a power conversion efficiency (PCE) of 18.3% and a crack-onset strain of 23.8%.
• The optimized terpolymer enhanced mechanical stretchability by increasing backbone twist and facilitating stress dissipation.
• The PM-BO10%:BTP-eC9 is-OSCs demonstrated excellent PCE retention (80% at 31.0% strain), reaching 14.2% PCE under strain.

Conclusions:

• The twisted terpolymer design strategy successfully improved both PCE and stretchability in is-OSCs.
• This approach offers a novel pathway for creating efficient and robust polymer donors for next-generation wearable electronics.
• The developed materials show significant potential for practical applications in flexible and stretchable power generation.