Resolving the Efficiency-Mechanical Trade-off in Organic Solar Cells: 20.4% Enabled by Hydrogen-Bonding Engineering.

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Organic solar cells (OSCs) typically face a trade-off between power conversion efficiency (PCE) and mechanical robustness.
• High mechanical toughness often requires amorphous polymers, which can negatively impact photovoltaic performance.

Purpose of the Study:

• To resolve the efficiency-robustness trade-off in organic solar cells (OSCs).
• To develop novel donor polymers that enhance both mechanical properties and photovoltaic performance.

Main Methods:

• Employing random copolymerization to incorporate ester-substituted thiophene units.
• Introducing hydroxyl (─OH) and urethane (─OOCNHC₆H₁₃) groups to induce hydrogen bonding.
• Synthesizing PM6-H, PM6-OH, and PM6-UR copolymers.

Main Results:

• Achieved a crack-onset strain (COS) exceeding 46% and a high PCE of up to 20.4%.
• Demonstrated superior storage, thermal, and light stability, with T₈₀ twice that of the PM6 benchmark.
• Fabricated flexible OSCs with 18.22% PCE and retained ~90% PCE after 2200 bending cycles.

Conclusions:

• Copolymerization with controlled hydrogen-bonding interactions effectively overcomes the efficiency-robustness trade-off in OSCs.
• The developed polymers offer a pathway to high-performance, mechanically durable, and stable OSCs for practical applications.