Polymeric white organic light-emitting diodes with two emission layers

Area of Science:

• Materials Science
• Organic Electronics
• Photonics

Background:

• White organic light-emitting diodes (WOLEDs) are crucial for next-generation displays and lighting.
• Achieving stable and efficient white light emission in polymer light-emitting diodes (PLEDs) remains a challenge.
• Multilayer structures offer a pathway to tune emission properties and improve device performance.

Purpose of the Study:

• To fabricate and characterize a novel WOLED device utilizing a multilayer emissive structure.
• To investigate the role of a PEDOT:PSS buffer layer in enhancing white light emission.
• To optimize device parameters for achieving CIE coordinates close to standard white light.

Main Methods:

• Fabrication of a multilayer PLED device with the structure ITO/PEDOT:PSS/Emissive layer/LiF/Al.
• The emissive layer comprised a blend of yellow-emitting Poly[9,9-dioctylfluorenyl-2,7-diyl]-co-1,4-benzo-(2,1,3)-thiadiazole (F8BT) and blue-emitting Poly[9,9-di-(2'-ethylhexyl)fluorenyl-2,7-diyl] (BEHF).
• A PEDOT:PSS buffer layer was introduced between the emissive layers, and solution processing techniques were employed.

Main Results:

• The fabricated WOLED device achieved a brightness of 280 cd/m2 and an emission efficiency of 1.18 cd/A at 12.6 V.
• The device with a doped PEDOT:PSS layer and a thicker blue-emission layer exhibited CIE color coordinates of (0.30, 0.34).
• These coordinates are notably close to the standard white coordinates of (0.33, 0.33).

Conclusions:

• The integration of a PEDOT:PSS buffer layer effectively facilitates the solution processing of multilayer PLEDs.
• The developed multilayer structure enables efficient white light emission with color coordinates approaching the standard white point.
• This study presents a promising approach for the development of high-performance WOLEDs for display and lighting applications.