Stable Ultrabroad-Absorbing Radical Achieves Efficient NIR-II Photothermal Conversion via Facile Synthesis.

Area of Science:

• Materials Science
• Organic Electronics
• Photochemistry

Background:

• Nitroxide radicals possess strong electron-withdrawing properties, inspiring new material designs.
• Conventional organic electronics often rely on closed-shell materials, limiting their potential applications.

Purpose of the Study:

• To synthesize and characterize a novel open-shell material, EDOT-TPAO4, inspired by nitroxide radicals.
• To investigate the photothermal conversion and solar-driven water evaporation capabilities of EDOT-TPAO4.
• To establish a new molecular design strategy for radical-based electron acceptors and semiconductors.

Main Methods:

• One-step demethylation and oxidation of EDOT-TPAOMe4 to synthesize EDOT-TPAO4.
• Time-dependent density functional theory (TD-DFT) calculations to determine electronic structure.
• Optical absorption, electrical conductivity, electrochemical stability, photothermal conversion efficiency, and solar-driven water evaporation measurements.

Main Results:

• EDOT-TPAO4 exhibits an acceptor-donor-acceptor configuration with radical termini acting as electron acceptors.
• The optical bandgap is significantly reduced from 2.74 eV (EDOT-TPAOMe4) to 1.26 eV (EDOT-TPAO4).
• Achieved high electrical conductivity (0.02 S cm⁻¹), broad absorption (300-2500 nm), rapid photothermal conversion (290 °C in 60 s), and efficient solar-driven water evaporation (1.433 kg m⁻² h⁻¹).

Conclusions:

• EDOT-TPAO4 is a highly efficient and stable organic photothermal material with excellent solar-driven water evaporation capabilities.
• The study introduces a novel molecular design strategy for next-generation radical-based electron acceptors and open-shell semiconductors.
• This work challenges conventional closed-shell strategies in organic electronics, paving the way for new functional materials.