A New Lridium(III) Complex as a Deep-Red Phosphorescent Emitter in Organic Light-Emitting Diodes

Area of Science:

• Materials Science
• Organic Electronics
• Photochemistry

Background:

• Phosphorescent organic light-emitting diodes (PhOLEDs) are crucial for energy-efficient displays and lighting.
• Developing novel phosphorescent emitters with high efficiency and specific emission colors is an ongoing research area.
• Iridium(III) complexes are widely studied for their strong phosphorescence and tunable electronic properties.

Purpose of the Study:

• To synthesize and characterize a novel red-emitting iridium(III) complex, bis[2-(5-(9H-carbazole-9-yl)thiophene-2-yl)benzo[d]thiazole]iridium(III)acetylacetonate ([(CTBT)2Ir(acac)]).
• To evaluate the photophysical and electrochemical properties of the synthesized complex.
• To fabricate and assess the performance of phosphorescent organic light-emitting diodes (PhOLEDs) utilizing the novel iridium(III) complex as a dopant.

Main Methods:

• Synthesis of the iridium(III) complex [(CTBT)2Ir(acac)].
• Characterization using photoluminescence (PL) spectroscopy and cyclic voltammetry to determine photophysical and electrochemical properties.
• Fabrication of PhOLED devices with a specific multilayer structure (ITO/PEDOT:PSS/TAPC/TPBi:TCTA:dopant/TSPO1/LiF/Al).
• Device performance evaluation, including luminous efficiency, external quantum efficiency, luminance, and power efficiency.

Main Results:

• The synthesized [(CTBT)2Ir(acac)] complex exhibits photoluminescence emission at 630 nm.
• Calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels are -5.14 eV and -2.83 eV, respectively.
• The fabricated device doped with 5% [(CTBT)2Ir(acac)] achieved a high luminous efficiency of 2.06 cd/A, maximum external quantum efficiency of 4.32%, maximum luminance of 398.8 cd/m², and power efficiency of 1.79 lm/W.
• The device demonstrated Commission Internationale de L'Eclairage (CIE) coordinates of (0.69, 0.31), indicating red emission.

Conclusions:

• The novel red-emitting iridium(III) complex [(CTBT)2Ir(acac)] is a promising material for phosphorescent organic light-emitting diodes.
• The synthesized complex possesses suitable photophysical and electrochemical properties for efficient light emission.
• The fabricated PhOLED device demonstrates competitive performance metrics, validating the potential of [(CTBT)2Ir(acac)] for red emission applications.