Novel Ir(III) Complexes with NHC-Based Ancillary Ligands for Efficient Nondoped OLEDs

Area of Science:

• Materials Science
• Organic Electronics
• Photochemistry

Background:

• Nondoped organic light-emitting diodes (OLEDs) are crucial for displays and lighting due to their simple fabrication and stability.
• Achieving high electroluminescence (EL) performance and low turn-on voltage in nondoped OLEDs remains a challenge.

Purpose of the Study:

• To develop novel iridium(III) complexes as efficient emitters for nondoped OLEDs.
• To investigate the impact of electron-deficient substituents on ligand performance in OLED devices.

Main Methods:

• Synthesis of three iridium(III) complexes with N-heterocyclic carbene (NHC) auxiliary ligands functionalized with sulfonyl or phosphine oxide groups.
• Fabrication and characterization of nondoped and doped OLED devices using these complexes.
• Analysis of electroluminescence performance, including turn-on voltage and efficiency.

Main Results:

• All synthesized Ir(III) complexes exhibited green emission and good neat film efficiency.
• Nondoped device N3, utilizing tBu-Ir-ISO, showed superior EL performance with a low turn-on voltage (2.1 V), high power efficiency (30.7 lm W⁻¹), and current efficiency (27.0 cd A⁻¹).
• Electron-deficient substituents on NHC ligands contributed to steric hindrance and balanced charge transport, enhancing device performance.

Conclusions:

• The developed Ir(III) complexes are promising emitters for high-performance nondoped OLEDs.
• The strategy of incorporating electron-deficient groups onto NHC ligands is effective for improving OLED efficiency.
• The findings offer a straightforward approach for designing advanced Ir(III) complexes for phosphorescent OLED applications.