Suppression of efficiency roll-off in solution-processed OLEDs using pyrimidine-based iridium complexes modified with...

Area of Science:

• Materials Science
• Organic Chemistry
• Photophysics

Background:

• Bis-cyclometalated iridium complexes are crucial for organic light-emitting diodes (OLEDs).
• Minimizing intermolecular interactions is key to improving device efficiency and stability.

Purpose of the Study:

• To synthesize novel bis-cyclometalated iridium complexes with enhanced photophysical properties.
• To investigate the impact of steric spacers on self-quenching and device performance.

Main Methods:

• Mild reaction conditions for the synthesis of three iridium complexes (Ir1-Ir3).
• Photoluminescence quantum efficiency (PLQY) measurements.
• Fabrication and characterization of electroluminescence devices.

Main Results:

• All complexes showed emission peaks between 507-509 nm with high PLQY (69-97%).
• Steric spacers effectively reduced self-quenching and bimolecular interactions.
• The Ir3-based device achieved a luminous efficiency of 39.6 cd A⁻¹, a high external quantum efficiency (EQE) of 13.1%, and a low efficiency roll-off (4.2% at 1000 cd m⁻²).

Conclusions:

• The synthesized iridium complexes exhibit excellent photoluminescence and electroluminescence properties.
• Steric pinene spacers significantly suppress intermolecular interactions, leading to improved device efficiency and stability.
• These findings suggest potential for developing advanced OLED materials.