The Important Role of Carbonyl in Accelerating Reverse Intersystem Crossing for Selenium-Based Organoboron Narrowband...

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Narrowband emissive polycyclic aromatic heterocycles (PAHs) with multiple resonance thermally-activated delayed fluorescence (MR-TADF) offer high color purity and efficiency.
• Thermally-activated reverse intersystem crossing (RISC) is often limited by large energy gaps and weak spin-orbital coupling in MR-TADF molecules.

Purpose of the Study:

• To develop novel organoboron PAHs for efficient blue light emission.
• To overcome the rate-limiting step of thermally-activated RISC in MR-TADF materials.
• To investigate the impact of selenium doping and carbonyl incorporation on photophysical properties.

Main Methods:

• Synthesis of three novel carbonyl-containing organoboron PAHs doped with selenium atoms (pSeXBNO, 1pSeXBN, and pSeXBN).
• Characterization of their photophysical properties, including singlet-triplet energy gap (ΔE_ST) and RISC rates.
• Fabrication and testing of non-sensitized and bi-color white organic light-emitting diodes (OLEDs) using the synthesized materials.

Main Results:

• Selenium-embedded carbonyl heterocycles significantly reduced ΔE_ST and enabled ultrafast RISC rates (up to 4.8 × 10⁷ s^-1).
• The OLED device using pSeXBN achieved a peak emission at 478 nm with a narrow bandwidth of 28 nm.
• Maximum external quantum efficiency (EQE) reached 32.6% for blue OLEDs and 30.9% for white OLEDs, with excellent efficiency retention.

Conclusions:

• The incorporation of selenium and carbonyl groups in organoboron PAHs is a promising strategy for developing high-performance blue MR-TADF materials.
• These materials demonstrate state-of-the-art performance for narrowband blue and white OLEDs.
• The study highlights the guiding role of carbonyl groups in advancing narrowband blue emitters.