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Proceedings Paper

Light-emitting diodes with naphtalimide side-chain polymers: basic properties and role of polymer thickness in two-layer devices
Author(s): Franco Cacialli; Cecile-Maria Bouche; Pierre L. Le Barny; Hugues Facoetti; Francoise Soyer; Philippe Robin; Richard H. Friend
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Paper Abstract

We report the fabrication of efficient green light-emitting diodes using a side-chain polymer based on a high-electron affinity (EA) naphtalimide moiety (PNI). The chromophore is attached to a polymethacrylate backbone through a spacer, and emits in the green with high efficiency. In single-layer light-emitting diodes (LEDs), we find that the electroluminescence (EL) efficiency is not limited by Al cathodes as for poly(p-phenylene-vinylene), PPV, and we attribute this to the increased EA. We report maximum internal efficiencies of about 1.7 percent for Ca and 0.9 percent for Al in double-layer devices where PPV serves as both Hole-injector and emitter. Compared to some oxadiazole based electron injection/transport layer, PNI gives higher efficiencies at high currents, and longer lifetimes. Tuning of emission in the red is possible by dye-doping the PNI and causing the emission to happen in this layer. We discuss the properties of the different device configurations with a view to the electronic structure of the materials and in particular to the influence of the thickness of the individual layers on efficiency and driving conditions.

Paper Details

Date Published: 1 December 1997
PDF: 8 pages
Proc. SPIE 3148, Organic Light-Emitting Materials and Devices, (1 December 1997); doi: 10.1117/12.284173
Show Author Affiliations
Franco Cacialli, Cambridge Univ. (United Kingdom)
Cecile-Maria Bouche, Thomson-CSF (France)
Pierre L. Le Barny, Thomson-CSF (France)
Hugues Facoetti, Thomson-CSF (France)
Francoise Soyer, Thomson-CSF (France)
Philippe Robin, Thomson-CSF (France)
Richard H. Friend, Cambridge Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 3148:
Organic Light-Emitting Materials and Devices
Zakya H. Kafafi, Editor(s)

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