Ag(i) emitters with ultrafast spin-flip dynamics for high-efficiency electroluminescence

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Carbene-metal-amide (CMA) complexes are promising emitters for organic light-emitting diodes (OLEDs).
• Limited research exists on silver(i)-CMA complexes, especially their electroluminescent properties.
• Developing efficient and stable emitters is crucial for advancing OLED technology.

Purpose of the Study:

• To synthesize and characterize novel silver(i)-CMA complexes using benzothiophene-fused carbazole ligands.
• To investigate the photophysical properties, including emission mechanisms and lifetimes, of these Ag(i)-CMA complexes.
• To evaluate the performance of OLEDs fabricated using these complexes as emitters.

Main Methods:

• Synthesis of a series of Ag(i)-CMA complexes.
• Photoluminescence quantum yield (PLQY) measurements in thin films.
• Transient absorption spectroscopy to study spin-flip dynamics.
• Fabrication and characterization of solution-processed OLED devices.

Main Results:

• The synthesized Ag(i)-CMA complexes exhibit thermally activated delayed fluorescence (TADF).
• High photoluminescence quantum yields (PLQY) up to 72% were achieved in thin films.
• Ultrashort emission lifetimes (down to 11 ns in solution, 144 ns in films) were realized by enhancing ligand π-donating ability.
• Record external quantum efficiencies (EQEs) of 16.2% (max) and 13.4% (at 1000 nits) were achieved in solution-processed OLEDs.
• Ultrafast spin-flip dynamics with high forward and reverse intersystem crossing rates were confirmed.

Conclusions:

• This work demonstrates an effective strategy for developing short-lived TADF materials based on Ag(i)-CMA complexes.
• The developed complexes represent state-of-the-art performance for silver(i) emitters in OLEDs.
• These findings pave the way for high-efficiency, solution-processed OLEDs using novel Ag(i)-CMA emitters.