Linearly polarised organic light-emitting diodes (OLEDs): synthesis and characterisation of a novel hole-transporting photoalignment copolymer

• Main Authors: Aldred, M.P., Vlachos, P., Contoret, A.E.A., Farrar, S.R., Chung-Tsoi, W., Mansoor, B., Woon, K.L., Hudson, R., Kelly, S.M., O'Neill, M.
• Format: Article
• Published: Royal Society of Chemistry 2005
• Subjects: Q Science (General); QC Physics
• Online Access: http://eprints.um.edu.my/12891/; http://pubs.rsc.org/en/Content/ArticleLanding/2005/JM/B506063J#!divAbstract; http://dx.doi.org/10.1039/B506063J

We describe the synthesis and characterisation of a novel hole transporting photoalignment copolymer for linearly polarised emission. The copolymer has a coumarin side-chain which undergoes (2 + 2) cycloaddition on irradiation with ultraviolet light. A fluorene side-chain, whose ionisation potential is well matched to the work-function of indium tin oxide, provides hole transporting properties. Polarised green electroluminescence was obtained by spin coating a novel polymerisable and light-emitting liquid crystal onto the photoaligned copolymer. A polarisation ratio value of 13 : 1 and a polarised irradiance of 200 cd m−2 was obtained at 9 V. Polarised red emission is also described in a guest–host configuration. The spatial patterning of the polarisation direction is also shown.