Fully Planarized Donor Enables Record-High Efficiency for Blue Through-Space Charge Transfer Emission

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Thermally activated delayed fluorescence (TADF) materials are crucial for efficient organic light-emitting diodes (OLEDs).
• Through-space charge transfer (TSCT) emitters offer a promising architecture for TADF materials.
• Developing high-performance blue TSCT emitters is challenging due to the trade-off between wide bandgap and electronic interactions.

Purpose of the Study:

• To design and synthesize a novel blue TSCT emitter with enhanced performance.
• To investigate the impact of a fully planarized donor structure on TSCT emitter properties.
• To achieve state-of-the-art external quantum efficiencies (EQEs) in blue OLEDs and hyperfluorescent devices.

Main Methods:

• Synthesis of a novel TSCT emitter featuring a fully planarized donor.
• Photophysical characterization including photoluminescence quantum yield (PLQY) and reverse intersystem crossing (RISC) rate measurements.
• Fabrication and characterization of OLEDs and hyperfluorescent devices using the developed emitter.

Main Results:

• The novel TSCT emitter exhibits an emission peak at 467 nm, 98% PLQY, and a high RISC rate of 1.8×10^6 s^-1.
• OLEDs achieved a maximum EQE of 34.0% with CIE coordinates (0.16, 0.29) and luminance of 21560 cd m^-2.
• Hyperfluorescent devices showed a high EQE of 35.8% with narrow FWHM (20 nm) and CIE coordinates (0.12, 0.14).

Conclusions:

• A fully planarized donor is critical for developing high-efficiency blue TSCT emitters.
• The developed TSCT emitter represents a significant advancement for blue OLED and hyperfluorescent applications.
• This work provides a new strategy for designing next-generation organic optoelectronic materials.