Photoinduced radical emission from flexible organic crystals

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Organic single crystals (OSCs) offer unique optical properties and flexibility for devices.
• Fabricating flexible OSCs with radical luminescence is challenging due to non-emissive radicals in condensed states.

Purpose of the Study:

• To develop a strategy for creating flexible OSCs with simultaneous radical emission and flexibility.
• To investigate a photoactivated radical self-doping approach for OSCs.

Main Methods:

• Utilized UV irradiation in air on a naphthyl benzoate derivative (NPBr) to induce photodissociation.
• Employed experimental and theoretical analyses to understand luminescence origins and crystal properties.
• Characterized the material's flexibility, photoluminescence quantum yield (PLQY), and optical waveguide performance.

Main Results:

• Achieved a 60-fold enhancement in blue fluorescence (PLQY from 0.8% to 47.7%) in NPBr crystals post-irradiation.
• Identified oxygen-centered radicals, generated via photodissociation and stabilized within the crystal matrix, as the source of luminescence.
• Demonstrated high elasticity (~9.76 GPa Young's modulus) and bendability, enabling function as low-loss flexible optical waveguides.

Conclusions:

• The photoactivated radical self-doping strategy successfully creates flexible OSCs with intense radical luminescence.
• This method concurrently generates stable radicals and preserves crystal flexibility, offering a universal approach for designing advanced luminescent materials.