Flexible Organic Radical Cocrystal With 94% Photothermal Conversion Efficiency

Area of Science:

• Materials Science
• Organic Electronics
• Photothermal Conversion

Background:

• Flexible photothermal materials often face interfacial incompatibility issues, leading to poor long-term stability and performance.
• Existing composite materials struggle to balance interfacial stability with high photothermal efficiency.

Purpose of the Study:

• To develop a novel flexible photothermal material with enhanced interfacial stability and high performance.
• To explore the potential of flexible organic crystals for efficient solar energy harvesting.

Main Methods:

• Cocrystallization of electron donor perylene (PE) and acceptor naphthalene diimide (NDI) to form flexible PE-NDI organic crystals.
• Characterization of radical characteristics, light absorption, mechanical properties, and photothermal conversion efficiency.
• Integration into a thermoelectric generator for photo-thermo-electric conversion.

Main Results:

• Achieved centimeter-size, mechanically flexible PE-NDI cocrystals with persistent radical characteristics (2.1 µs spin coherence time).
• Demonstrated strong light absorption (200-780 nm) due to prominent donor-acceptor interaction (-87.7 kJ mol⁻¹).
• Obtained an exceptionally high photothermal conversion efficiency of 94% at 685 nm excitation and observed reversible elastic bending.

Conclusions:

• Flexible organic crystals, specifically PE-NDI cocrystals, offer a promising single-component solution for stable and efficient photothermal materials.
• These materials enable direct solar energy harvesting through photo-thermo-electric conversion, highlighting their potential in renewable energy applications.
• The study underscores the untapped potential of mechanically compliant organic crystals for lightweight, high-performance photothermal applications.