White OLED in Hybrid Structure for Enhancing Color Purity

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Organic Light Emitting Diodes (OLEDs) are crucial for advanced display and lighting technologies.
• Achieving stable and efficient white emission in OLEDs requires careful selection and integration of phosphorescent and fluorescent emitters.
• Controlling charge balance and recombination zones is key to optimizing OLED performance.

Purpose of the Study:

• To synthesize novel red and blue emitting materials for white OLEDs.
• To fabricate and characterize white OLED devices utilizing these materials.
• To investigate the impact of a hole blocking layer's thickness on device performance.

Main Methods:

• Synthesis of bis(1,4-bis(5-phenyloxazol-2-yl)phenyl) iridium(picolate) [Ir-complexes] for red emission.
• Synthesis of bis (2-(2-hydroxyphenyl) benzoxazolate)zinc [Zn(HPB)2] for blue emission.
• Fabrication of white OLEDs using Zn(HPB)2, Ir-complexes, tris (8-hydroxy quinoline)aluminum [Alq3], and varying thicknesses of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline [BCP] as a hole blocking layer.

Main Results:

• White OLEDs were successfully fabricated using a double emitting layer structure (Zn(HPB)2 and Alq3:Ir-complexes).
• Optimal white emission was achieved when the BCP hole blocking layer thickness was 5 nm.
• A maximum luminance of 5400 cd/m2 at 650 mA/cm2 and CIE coordinates of (0.339, 0.323) at 10 V were obtained.

Conclusions:

• The developed Ir-complexes and Zn(HPB)2 are suitable for fabricating efficient white OLEDs.
• The BCP layer thickness critically influences white emission characteristics.
• The study demonstrates a viable approach for high-performance white OLED device engineering.