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Photoacid cross-linkable polyfluorenes for optoelectronics applications

Charas, A. ; Alves, H. ; Martinho, J. ; Alcácer, L. ; Fenwick, O. ; Cacialli, F. ; Morgado, J.

Synthetic Metals Vol. 158, Nº , pp. 643 - 653, September, 2008.

ISSN (print): 0379-6779
ISSN (online):

Journal Impact Factor: 1,962 (in 2008)

Digital Object Identifier: 10.1016/j.synthmet.2008.02.016

Polyfluorene copolymers are functionalised with oxetane side groups which make them cross-linkable
upon exposure to an acid. Upon addition of a photoacid they become photo-cross-linkable if exposed
to UV light. Optical and electrochemical properties of these copolymers, both in the soluble and crosslinked
forms are compared.We further show that the use of this type of copolymer allows the fabrication
of multilayer structures without restriction of the organic solvent used to deposit an upper layer. In
particular, we fabricate multilayer LEDs with enhanced luminous efficiency using one of the copolymers.
The possibility to photo-cross-link these materials is also used to prepare micrometer size patterns, using
a transmission electron microscope grid as a shadow mask. Furthermore, the use of a scanning near-field
optical microscope allows submicron patterns to be prepared.We propose that this approach, which can
be extended to a wide range of conjugated polymers, can be useful for the fabrication of optical, electronic
and optoelectronic structures.