Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Thermally activated delayed fluorescence (TADF) materials are crucial for efficient organic light-emitting diodes (OLEDs).
• Multiresonant TADF (MR-TADF) compounds offer unique photophysical properties but can be limited by their structural rigidity.
• Ionic emitters present a pathway to tune electronic properties and solubility.

Purpose of the Study:

• To design and synthesize novel ionic TADF emitters as charged analogues of the MR-TADF compound DiKTa.
• To investigate the photophysical properties and emission characteristics of these new ionic emitters.
• To evaluate the performance of these emitters in light-emitting electrochemical cells (LECs).

Main Methods:

• Synthesis of two ionic TADF emitters: DiKTa-OBuIm and DiKTa-DPA-OBuIm.
• Photoluminescence spectroscopy to determine emission wavelengths and quantum yields.
• Time-resolved photoluminescence spectroscopy to measure delayed lifetimes.
• Fabrication and characterization of light-emitting electrochemical cells (LECs).

Main Results:

• The synthesized ionic emitters, DiKTa-OBuIm and DiKTa-DPA-OBuIm, exhibit red-shifted emission compared to the parent DiKTa compound.
• DiKTa-OBuIm emits in the green region (λ_PL = 499 nm) and DiKTa-DPA-OBuIm emits in the red region (λ_PL = 577 nm).
• Both emitters demonstrate high photoluminescence quantum yields (71% and 61%) and efficient delayed lifetimes (316.6 μs and 241.7 μs).
• LECs fabricated with these emitters successfully produced green (λ_max = 534 nm) and red (λ_max = 656 nm) light.

Conclusions:

• The developed ionic TADF emitters are effective for achieving distinct green and red emissions.
• These compounds show promising photophysical properties, including high quantum yields and long delayed lifetimes.
• The successful implementation in LECs highlights their potential for next-generation display and lighting technologies.