Chlorine-Enabled Double Borylation Strategy for π-Extended MR-TADF Emitters: From Synthetic Challenge to Benchmark...

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Thermally activated delayed fluorescence (TADF) materials are crucial for high-efficiency organic light-emitting diodes (OLEDs).
• Achieving pure-green, narrowband emission with excellent stability in TADF emitters for displays remains a significant challenge.
• Existing synthetic routes often struggle with complex π-extended frameworks.

Purpose of the Study:

• To develop a novel and efficient synthetic strategy for π-extended multiple resonance (MR) TADF materials.
• To overcome synthetic limitations in accessing previously inaccessible MR-TADF frameworks.
• To create a versatile platform for developing high-performance, color-tunable green TADF emitters for OLED applications.

Main Methods:

• A one-shot double borylation strategy utilizing chlorine substituents for regioselective synthesis.
• Synthesis of a key intermediate, W-DABNA-Cl, via the developed borylation method.
• Late-stage diversification of the intermediate to generate a series of MR-TADF emitters.

Main Results:

• Successful synthesis of a π-extended MR framework previously considered synthetically inaccessible.
• Generation of diverse MR-TADF emitters with narrowband green to yellow-green emission (FWHM 27-34 nm).
• Fabrication of TADF-sensitized fluorescence OLED devices achieving a maximum external quantum efficiency (EQE) of 36.1% and superior efficiency-brightness stability.

Conclusions:

• The developed synthetic strategy overcomes key bottlenecks in MR-TADF material synthesis.
• The new platform enables the creation of color-tunable TADF emitters with excellent photophysical properties.
• This work paves the way for high-performance, stable green OLEDs suitable for advanced display technologies.