Meta Junction Promoting Efficient Thermally Activated Delayed Fluorescence in Donor-Acceptor Conjugated Polymers

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Donor-acceptor (D-A) conjugated polymers are key materials for organic light-emitting diodes (OLEDs).
• Achieving efficient thermally activated delayed fluorescence (TADF) is crucial for high-performance OLEDs.
• Tuning the electronic properties of D-A polymers can enhance TADF efficiency.

Purpose of the Study:

• To investigate the effect of meta-junctions in D-A conjugated polymers on TADF properties.
• To develop novel D-A polymers with enhanced TADF for OLED applications.
• To demonstrate the potential of meta-linked polymers for efficient light emission.

Main Methods:

• Synthesis of a series of D-A conjugated polymers with varying connection sites (para vs. meta).
• Characterization of photophysical properties, including singlet-triplet energy splitting (ΔE_ST).
• Fabrication and testing of solution-processed OLED devices using the synthesized polymers.

Main Results:

• Meta-linked D-A polymers exhibited significantly reduced ΔE_ST (0.10 eV) compared to para-linked analogues (0.44 eV) due to increased hole-electron separation.
• The meta-linked polymer demonstrated strong delayed fluorescence, unlike its para-linked counterpart.
• OLEDs fabricated with the meta-linked polymer achieved a promising external quantum efficiency (EQE) of 15.4%.

Conclusions:

• The meta-junction is an effective strategy for realizing efficient TADF in D-A conjugated polymers.
• Tuning the linkage position in D-A polymers offers a pathway to control photophysical properties and improve OLED performance.
• These findings highlight the potential of meta-linked D-A conjugated polymers for next-generation TADF OLEDs.