High-Efficiency Red Electroluminescence Based on a Carbene-Cu(I)-Acridine Complex.

Area of Science:

• Materials Science
• Chemistry
• Physics

Background:

• Developing efficient red-emitting organometallics, particularly those based on earth-abundant copper(I), presents significant challenges for organic light-emitting diodes (OLEDs).
• Copper(I) complexes often suffer from weak spin-orbit coupling and substantial excited-state reorganization, hindering their performance.

Purpose of the Study:

• To design and synthesize a novel copper(I) complex for efficient red emission in OLEDs.
• To investigate the photophysical properties and device performance of the developed copper(I) complex.

Main Methods:

• Synthesis of a new copper(I) complex, MAC*-Cu-DPAC, utilizing a rigid 9,9-diphenyl-9,10-dihydroacridine donor ligand within a carbene-metal-amide framework.
• Characterization of the complex's photoluminescence, excited-state lifetime, and geometric and conformational properties.
• Fabrication and testing of OLED devices incorporating the MAC*-Cu-DPAC complex.

Main Results:

• The MAC*-Cu-DPAC complex demonstrated efficient red emission with a high photoluminescence quantum yield (PLQY) of up to 70% and a sub-microsecond excited-state lifetime.
• The complex exhibited a high horizontal dipole ratio (HDR) of 77%, attributed to its linear geometry and coplanar ligand conformation, a first for coinage metal(I) complexes.
• OLEDs fabricated with this complex achieved high external quantum efficiencies (EQEs) of 21.1% (maximum) and 20.1% at 1000 nits, with emission peaking at approximately 630 nm.

Conclusions:

• The developed MAC*-Cu-DPAC complex represents a significant advancement in red-emitting materials for OLEDs.
• The findings highlight the potential of carbene-metal-amide copper(I) complexes with rigid ligands for achieving state-of-the-art OLED performance.
• This work offers a promising pathway for the development of efficient and stable red OLEDs using earth-abundant metals.