Alcohol-soluble conjugated poly(fluorene-co-thiophene) as an electron-transport material for polymer light-emitting diodes

ABSTRACT

A series of alternating polyfluorene copolymers containing fluorene (P1-OF), bithiophene (P2-BT), and thiophene (P3-TH) moieties have been synthesized via a palladium-catalyzed Suzuki coupling reaction. Among them, the P3-TH polymer highly contains hydroxyl groups which provides enough solubility in polar solvents such as alcohols and dimethylformamide. Multilayer polymer light-emitting diodes have been fabricated using a semiconducting polymer, F8BT, as an emissive layer and the methanol-soluble P3-TH as an electron-transport layer. By the device configuration of ITO/PEDOT/TFB/F8BT/P3-TH/LiF/Al, it shows a luminescence efficiency of 1.48 cd/A and a turn-on voltage of 4.6 V. The emission with maxima at 448 nm and 495 nm which fell in the blue region with the CIE coordinates (x = 0.18, y = 0.24).

KEYWORDS:

• Electron-transport layer
• luminescence efficiency
• multilayer processing
• polyfluorenes
• polymer light-emitting diodes

Acknowledgment

This work was supported by University Research Program in Hannam University (2017).