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Luminescence properties of poly(9,9-dioctylfluorene)/polyvinylcarbazole blends: Role of composition on the emission colour stability and electroluminescence efficiency

Bernardo , G. ; Charas, A. ; Morgado, J.

Journal of Physics and Chemistry of Solids Vol. 71, Nº 3, pp. 340 - 345, March, 2010.

ISSN (print): 0022-3697
ISSN (online):

Journal Impact Factor: 1,103 (in 2008)

Digital Object Identifier: 10.1016/j.jpcs.2009.12.087

Abstract
Light-emitting diodes (LEDs), based on blue-emitting polyfluorenes are usually prone to the appearance of a contaminant green emission (centered around 520 nm), leading to an apparent whitish light emission. We find that, for LEDs based on poly(9,9-dioctylfluorene), PFO, the blending with the hole transporting polyvinylcarbazole, PVK, can suppress such green emission. LEDs based on a PFO/PVK blend with a 1:2 weight ratio and with aluminum cathodes show a quite stable blue emission. This result reveals the important role played by the interchain interactions on the observed contaminant green emission. In addition, we observe that in Al-based devices blending causes a decrease in EL efficiency while in Mg-based devices we obtained higher efficiencies with the blend PFO:3PVK when comparing with neat PFO-based devices.