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Title: Phosphorescent conjugated polymers for light-emitting diodes
Author: Evans, N. R.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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This dissertation describes work done to improve the efficiency of conjugated-polymer organic light-emitting diodes (OLEDs) by harvesting both singlet and triplet excitons as electroluminescence. The electroluminescence quantum efficiencies of OLEDs based on the fluorescent conjugated polymer poly(9,9-dioctyl-9H-fluorene-2,7-diyl) 1.08 have been improved through the design, synthesis and application of new phosphorescent conjugated polymers. A study of simple blends of phosphorescent dopants with the polymer 1.08 showed that the red-phosphorescent dopant 2.15 is better suited for observing phosphorescent emission in a blend with the polymer 1.08 than are green- or orange-phosphorescent dopants. (Fig 8453A) The problem of phase separation in the simple blends was solved by tethering the red-phosphorescent dopants to the polyfluorene chains, to give the new phosphorescent conjugated copolymer 3.30. The maximum electroluminescence efficiencies in OLEDs of the copolymer 3.30, are greater than those of the corresponding fluorescent conjugated polymer, and typically an order of magnitude greater than those of the corresponding simple blends. (Fig. 8453B) Dexter triplet-energy transfer reduces the photoluminescence efficiency of copolymers in which the red-phosphorescent dopants are bonded directly to the polyfluorene chains - a nonconjugated manner but without the separation of a tether. In addition, the polymerisation of monomers with small singlet-triplet energy gaps has been proposed as a route for the synthesis of conjugated polymers with small singlet-triplet energy gaps, and some preliminary results are presented.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available