Carbonyl Functionalized Azaphosphinine-Based Multiple-Resonance Emitters via Regulated p/n/σ-π Hybrid Conjugation

Area of Science:

• Materials Science
• Organic Chemistry
• Optoelectronics

Background:

• Organic π-conjugated molecules (OCMs) are crucial for optoelectronic applications.
• Tuning electronic couplings in OCMs allows for fine-tuning of properties.
• Existing BN/CON emitters with p-π conjugation have limitations.

Purpose of the Study:

• To report the first example of hybrid COPN multiple-resonance (MR) thermally activated delayed fluorescence (TADF) emitters.
• To investigate the impact of P-center hyperconjugation on TADF properties.
• To explore the potential of these emitters in organic light-emitting diodes (OLEDs).

Main Methods:

• Modular synthesis protocols for creating hybrid COPN MR-TADF emitters.
• Analysis of electronic couplings, including n/σ/σ*-π* hyperconjugation and charge-transfer (CT) characteristics (SR and LR).
• Fabrication and testing of OLED devices using the developed emitters.

Main Results:

• New COPN MR-emitters demonstrate tunable TADF properties (FWHM, ISC/RISC, PLQY) influenced by P-regulated hyperconjugation.
• PO-derivative shows CON-type MR structure with short-range N➞CO CT.
• P(III)-derivative exhibits COP-type MR structure with long-range P➞CO CT.
• Double-PO derivative displays PON-type MR-TADF with N➞PO CT, achieving high PLQY (54%) and narrow FWHM (13 nm).
• OLED devices demonstrated narrow-band blue (FWHM: 26 nm) and cyan (FWHM: 17 nm) emission with high EQEs (7.3% and 22.8%).

Conclusions:

• Hybrid COPN MR-TADF emitters offer a new platform for designing advanced optoelectronic materials.
• The incorporation of p/n/σ-π coupling into OCMs significantly enhances TADF characteristics.
• These findings hold great promise for developing next-generation organic electronic devices with superior performance.