High-Efficiency Phosphorescent Hybrid Organic-Inorganic Light-Emitting Diodes Using a Solution-Processed...

Area of Science:

• Organic electronics
• Materials science
• Photophysics

Background:

• Organic light-emitting diodes (OLEDs) are crucial for display and lighting technologies.
• Improving the efficiency and charge transport properties of OLED materials is an ongoing research focus.

Purpose of the Study:

• To investigate the morphology, optical, and electrical properties of composite films made from 4,4',4″-tris(carbazol-9-yl)triphenylamine (TCTA) and 2,2'-(1,3-phenylene)bis[5-(4-tert-butylphenyl)-1,3,4-oxadiazole] (OXD-7).
• To compare the performance of solution-processed and vacuum-deposited films.
• To report high-efficiency hybrid OLED devices utilizing these composite films.

Main Methods:

• Fabrication of TCTA:OXD-7 composite films using both solution-processing and vacuum-deposition techniques.
• Characterization of film morphology, including surface smoothness and pinhole density.
• Evaluation of optical and electrical properties, focusing on carrier-transport characteristics.
• Fabrication and testing of monochromatic (blue, yellow, red) and white phosphorescent OLED devices.

Main Results:

• Both solution-processed and vacuum-deposited films exhibited smooth, pinhole-free morphology.
• Vacuum-deposited films demonstrated enhanced carrier-transport properties compared to solution-processed films.
• A strong correlation was established between carrier-transport properties and film packing density.
• High external quantum efficiencies were achieved for blue (18.9%), yellow (14.6%), and red (10.2%) devices.
• White devices achieved a maximum luminance efficiency of 40 cd A⁻¹ and a power efficiency of 20.8 lm W⁻¹ at 1000 cd m⁻².

Conclusions:

• Vacuum deposition offers advantages for achieving superior carrier transport in TCTA:OXD-7 composite films.
• The developed composite films enable high-efficiency monochromatic and white phosphorescent OLEDs.
• The achieved device efficiencies represent significant advancements over previously reported values, highlighting the potential of these materials.