Electroluminescence and hyperphosphorescence from stable blue Ir(III) carbene complexes with suppressed efficiency...

Area of Science:

• Materials Science
• Organic Electronics
• Photochemistry

Background:

• High-performance blue organic light-emitting diodes (OLEDs) are crucial for advanced display technologies.
• Achieving efficient and stable blue emission in OLEDs remains a significant challenge.
• Förster energy transfer from phosphorescent sensitizers to thermally activated delayed fluorescent (TADF) emitters offers a promising strategy.

Purpose of the Study:

• To design and synthesize novel iridium(III) metal complexes for efficient true-blue emission in OLEDs.
• To investigate the energy transfer mechanisms and photophysical properties of these complexes.
• To demonstrate the potential for mass production and high performance of blue OLEDs utilizing these materials.

Main Methods:

• Synthesis of four iridium(III) metal complexes (f-ct1a–d) with true-blue emission characteristics.
• Characterization of photophysical properties, including emission spectra and radiative decay lifetimes.
• Investigation of isomerization behavior in the presence of catalysts (sodium acetate, p-toluenesulfonic acid) at elevated temperatures.
• Fabrication and testing of a hyper-OLED device incorporating the developed emitters.

Main Results:

• The synthesized Ir(III) complexes exhibit efficient true-blue emissions and fast radiative decay lifetimes.
• Facile isomerization of the complexes was achieved under catalytic conditions at elevated temperatures, enabling decomposition-free mass production.
• The resulting hyper-OLED demonstrated a true-blue color (CIEy = 0.11) with a narrow spectral width (18 nm).
• The device achieved a maximum external quantum efficiency of 35.5% and maintained high efficiency (20.3%) at a high luminance of 5000 cd m⁻².

Conclusions:

• The developed iridium(III) complexes are highly suitable for efficient true-blue emissive OLEDs.
• The facile isomerization process facilitates scalable manufacturing of blue OLED emitters.
• These findings represent a significant advancement towards innovative and high-performance blue OLED technology.