Single-B/N MR-TADF emitters enhancing electroluminescence efficiency via a "terminal engineering" strategy

Area of Science:

• Materials Science
• Organic Electronics
• Photochemistry

Background:

• Single boron-nitrogen (BN) multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters face challenges with low efficiency and broad emission spectra.
• Terminal engineering offers a strategy to overcome these limitations in emitter design.

Purpose of the Study:

• To develop novel MR-TADF emitters with improved efficiency and narrowed emission spectra.
• To investigate the impact of terminal group functionalization on emitter performance.

Main Methods:

• Synthesized two novel MR-TADF emitters, DPA-CzBN and Indo-tCzBN, by incorporating diphenylamino and tert-butyl groups into BN frameworks.
• Characterized the photophysical properties, including photoluminescence quantum yield (PLQY) and full width at half maximum (FWHM).
• Fabricated and evaluated organic light-emitting diodes (OLEDs) using the developed emitters.

Main Results:

• Indo-tCzBN exhibited a narrow FWHM of 19 nm and a high PLQY of 97.5%.
• The horizontal dipole orientation factor (Θ//) for Indo-tCzBN reached 85.3%, significantly improving light outcoupling.
• OLEDs based on Indo-tCzBN achieved high maximum external quantum efficiencies (EQEmax) of 37.4% (non-sensitized) and 39.0% (sensitized).

Conclusions:

• The terminal engineering strategy is effective in enhancing the performance of single BN MR-TADF emitters.
• Indo-tCzBN represents a highly efficient MR-TADF emitter with potential for advanced OLED applications.
• The developed emitters achieve state-of-the-art performance for single BN molecular architectures.