Post-functionalized poly(N-vinylcarbazole)s as effective low turn-on-voltage phosphorescent-hosts in polymeric light emitting devices

DTAB-PVKs are prepared by post-functionalization of poly(N-vinylcarbazole) (PVK) with di(4-tolyl)aminobenzyl acetate (DTABOAc) as the pendant groups via the Friedel–Crafts reaction. Introduction of the methyl substituents at the para-position of DTABOAc is essential for suppression of its self-condensation. The details of the reactions mechanisms are elucidated by 1H NMR study. The Fermi level of DTAB-PVKs could be tuned by controlling the amounts of DTABOAc content in the polymer and DTAB-PVKs are found to be good hosts for phosphorescent polymer light-emitting diodes (PLEDs). In a device of PLED comprising PEDOT: PSS/DTAB-PVK-Ir(ppy)3-PBD/Mg–Ag, low turn on voltage at 6.5 V is found with a reasonably high current efficiency of 11.5 cd/A at 13.0 V. The power efficiency reaches 2.7 lm/W at 12.0 V. More importantly, the device performance related to the Fermi level of DTAB-PVKs.