Substituent effects of iridium complexes for highly efficient red OLEDs

Area of Science:

• Materials Science
• Photochemistry
• Organic Electronics

Background:

• Iridium complexes with 1-phenylisoquinoline ligands are utilized in organic light-emitting diodes (OLEDs).
• Tuning electronic properties through substituent modification is crucial for optimizing OLED performance.

Purpose of the Study:

• To investigate the substituent effects on the photophysical properties of iridium complexes.
• To evaluate the performance of these modified complexes in OLED devices.

Main Methods:

• Synthesis and characterization of iridium complexes with varying substituents on the 1-phenylisoquinoline ligand.
• Measurement of emission spectra, phosphorescence quantum yields, and excited-state lifetimes.
• Fabrication and testing of OLED devices using the synthesized complexes.

Main Results:

• Substituents significantly influenced emission peaks (598-635 nm), quantum yields (0.17-0.32), and lifetimes (1.07-2.34 µs).
• Substituents affected HOMO stability and mixing between 3π-π* and (3)MLCT states.
• An OLED device with tris [1-(4-fluoro-5-methylphenyl)isoquinolinato-C2,N]iridium(iii) achieved 15.5% external quantum efficiency and 12.4 lm W⁻¹ power efficiency.

Conclusions:

• Substituent modification offers a viable strategy to tune the photophysical properties of iridium complexes.
• The developed iridium complexes show promise for high-performance OLED applications.
• The study highlights the structure-property relationships governing excited-state decay kinetics and emission characteristics.