• Bown, Mark
• Hirai, Tadahiko
• Adhikari, Raju
• Postma, Almar
• Ueno, Kazunori

Abstract

This study reports on the synthesis of new thermally cross-linkable copolymers containing a reactive cross-linking comonomer. Synthesized polymers showed narrow molecular weight distribution (polydispersity) between 1.18 to 1.22 and 54 to 67% monomer conversion and incorporation of 2 to 7 mol% vinylbenzylcyclobutene comonomer. The polymer was soluble in nonpolar organic solvents such as chloroform, dichloromethane, toluene, and chlorobenzenes, and when cross-linked, showed resistance to solubility in the previously listed solvents. The cross-linked films exhibited uniform surface roughness below 1 nm. A polymer containing ~3.6 mol% vinylbenzylcyclobutene was thermally cross-linked and evaluated as a hole-transporting layer in green organic light-emitting diode devices. The devices showed a maximum current efficiency of 39.5 cd/A at a current density of 2.7 mA/cm2 and a brightness of 1000 cd/m2 with an International Commission on Illumination coordinate (0.33, 0.62). The device performances are found comparable with the ones with the conventional hole-transporting layer material, NPD.

Topics

• density
• surface
• reactive
• current density
• molecular weight
• copolymer
• polydispersity