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Thermally cross‐linkable copolymer and its evaluation as a hole transport layer in organic light‐emitting diode devices
Author(s) -
Adhikari Raju,
Postma Almar,
Li JuoHao,
Hirai Tadahiko,
Bown Mark,
Ueno Kazunori
Publication year - 2013
Publication title -
journal of the society for information display
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 52
eISSN - 1938-3657
pISSN - 1071-0922
DOI - 10.1002/jsid.159
Subject(s) - comonomer , materials science , polymer , copolymer , monomer , chlorobenzene , oled , chemical engineering , layer (electronics) , solubility , polymer chemistry , composite material , organic chemistry , chemistry , catalysis , engineering
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/cm 2 and a brightness of 1000 cd/m 2 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.