Phenphosphine-X(O, S, Se) locking multi-resonance thermally activated delayed fluorescence materials

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials are essential for high-efficiency, narrowband emission in displays.
• Organic light-emitting diodes (OLEDs) using MR-TADF emitters often face significant efficiency roll-off issues.

Purpose of the Study:

• To design novel MR-TADF emitters that overcome efficiency roll-off.
• To investigate the effect of a phenphosphine-X(O, S, Se) locking strategy with heavy atoms on reverse intersystem crossing (RISC) rates.
• To develop materials for ultra-high-definition displays.

Main Methods:

• Synthesis of three novel MR-TADF emitters: NBNPO, NBNPS, and NBNPSe.
• Characterization of photoluminescence properties in toluene, including emission wavelength and full-width at half-maximum (FWHM).
• Fabrication and testing of OLED devices to evaluate external quantum efficiencies (EQEs) and efficiency roll-off.

Main Results:

• Blue emission achieved with peaks at 468-471 nm and a narrow FWHM of 19 nm (0.11 eV).
• Doped films exhibited high photoluminescence efficiencies up to 95%.
• Accelerated RISC rates were observed: 5.92 × 10^4 s^-1 (NBNPO), 4.62 × 10^5 s^-1 (NBNPS), and 9.91 × 10^6 s^-1 (NBNPSe).
• Maximum EQEs reached 32.4% with reduced efficiency roll-off in the corresponding OLEDs.

Conclusions:

• The phenphosphine-X(O, S, Se) locking strategy effectively accelerates RISC, mitigating efficiency roll-off in MR-TADF OLEDs.
• These novel materials demonstrate significant potential for efficient and stable ultra-high-definition display applications.
• The study presents a promising molecular design approach for advanced organic electronic materials.