Azaborine as a Versatile Weak Donor for Thermally Activated Delayed Fluorescence

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Thermally activated delayed fluorescence (TADF) emitters are crucial for efficient organic light-emitting diodes (OLEDs).
• Developing pure-blue TADF emitters remains a significant challenge for lighting and display applications.
• Existing donor units like dimethylacridan (DMAC) and carbazole (Cz) have limitations for achieving optimal blue emission.

Purpose of the Study:

• To introduce a novel 1,4-azaborine (AZB) donor unit for designing blue TADF emitters.
• To investigate the photophysical properties and OLED performance of AZB-based TADF materials.
• To expand the chemical design strategies for high-performance blue donor-acceptor TADF systems.

Main Methods:

• Synthesis and characterization of novel AZB-based TADF molecules (AZB-Ph-TRZ and AZB-TRZ).
• Photophysical measurements including photoluminescence quantum yield (Φ_PL) and singlet-triplet energy gap (ΔE_ST).
• Fabrication and testing of OLED devices using the synthesized TADF emitters doped in mCP.

Main Results:

• AZB-Ph-TRZ exhibited a ΔE_ST of 0.39 eV, Φ_PL of 27%, and λ_PL of 415 nm.
• AZB-TRZ showed a reduced ΔE_ST of 0.01 eV and fast reverse intersystem crossing (k_RISC of 5 × 10⁶ s^-1).
• OLEDs with AZB-TRZ achieved sky-blue emission (CIE₁₉₃₁(x,y) of (0.22,0.39)) with a maximum external quantum efficiency (EQE_max) of 10.5%.

Conclusions:

• The novel AZB donor unit is effective for developing blue TADF emitters.
• AZB-based TADF materials offer promising performance for OLED applications.
• This work provides a new avenue for designing advanced blue-emitting TADF materials by pairing AZB with various acceptor groups.