Cascading Energy Transfer for Highly Efficient Deep-Red OLED Emission with Cyclometalated [3+2+1] Iridium Complexes

Area of Science:

• Materials Science
• Organic Electronics
• Photochemistry

Background:

• Cyclometalated iridium (III) complexes show promise for organic light-emitting diodes (OLEDs).
• Achieving efficient and stable deep-red emission is crucial for full-color displays and solid-state lighting.

Purpose of the Study:

• To design and synthesize novel [3+2+1] coordinated iridium (III) complexes for deep-red emission.
• To investigate the photophysical properties and device performance of these new emissive materials.

Main Methods:

• Synthesis of four novel iridium (III) complexes utilizing dibenzo[a,c]phenazine (dbpz) and monodentate ligands (-CN, -OCN).
• Characterization of photoluminescence quantum yields (PLQY) and emission spectra.
• Fabrication and testing of organic light-emitting diode (OLED) devices incorporating the synthesized complexes.

Main Results:

• Achieved deep-red emission in the range of 628-675 nm with high PLQYs up to 98%.
• Developed devices with deep-red color coordinates close to the ITU-R BT.2020 standard.
• Demonstrated high external quantum efficiencies (up to 20.7%) and good device stability.
• Observed cascading energy transfer processes in phosphorescent OLED devices, leading to pure red emission and high luminance (6471 cd m⁻²).

Conclusions:

• The rational molecular design strategy of [3+2+1] iridium complexes is effective for achieving highly efficient deep-red electrophosphorescent emission.
• The synthesized iridium (III) complexes offer significant potential for advanced display and lighting applications.