Optimizing the Intralayer and Interlayer Compatibility for High-Efficiency Blue Thermally Activated Delayed...

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Thermally activated delayed fluorescence (TADF) is crucial for efficient organic light-emitting diodes (OLEDs).
• Achieving high performance in blue TADF devices requires careful material design for host and electron transporting layers (ETLs).
• Intralayer and interlayer compatibility significantly impacts device efficiency and stability.

Purpose of the Study:

• To develop novel phosphine oxide-based host and electron transporting materials (ETMs) for high-performance blue TADF devices.
• To investigate the effect of molecular configuration and polarity on material compatibility and device performance.
• To optimize intralayer and interlayer compatibility for enhanced efficiency and stability.

Main Methods:

• Synthesis of phosphine oxide host materials: 4,6-bis(diphenylphosphoryl)dibenzothiophene (DBTDPO) and 4-diphenylphosphoryldibenzothiophene (DBTSPO).
• Synthesis of phosphine oxide ETMs: 2-(diphenylphosphoryl)dibenzothiophene sulfone (2DBSOSPO), 3-(diphenylphosphoryl)dibenzothiophene sulfone (3DBSOSPO), and 4-(diphenylphosphoryl)dibenzothiophene sulfone (4DBSOSPO).
• Fabrication and characterization of four-layer blue TADF devices incorporating these materials.

Main Results:

• DBTDPO demonstrated superior distribution uniformity with the blue TADF emitter DMAC-DPS compared to DBTSPO.
• 3DBSOSPO and 4DBSOSPO showed enhanced compatibility with host materials due to similar molecular polarity/configuration.
• ETMs exhibited excellent electron mobility (μe ~ 10⁻³ cm²/Vs) after molecular configuration tuning.
• Devices using DBTDPO and 4DBSOSPO achieved a maximum current efficiency of 33.5 cd/A and external quantum efficiency >17%.

Conclusions:

• Intralayer compatibility is key to achieving maximum device efficiencies.
• Interlayer compatibility plays a critical role in maintaining efficiency stability.
• The developed phosphine oxide materials offer a promising strategy for high-performance blue TADF devices.