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Durham University

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Publication details for Professor Andy Monkman

E. Stanislovaityte, J. Simokaitiene, S. Raisys, H. Al-Attar, J.V. Grazulevicius, A.P. Monkman & V. Jankus (2013). Carbazole based polymers as hosts for blue iridium emitters: synthesis, photophysics and high efficiency PLEDs. Journal of Materials Chemistry C 1(48): 8209-8221.

Author(s) from Durham

Abstract

This article reports the synthesis of new carbazole based polymers and their application as hosts in sky-blue polymer light emitting devices (PLEDs) with a solution-processed emitting layer doped with a cyclometalated Ir(III) complex. We systematically investigate their effect on the PLED performance. A current efficiency of 19.7 cd A(-1) and a brightness of 1850 cd m(-2) were achieved with these polymers. The roll-off in electrophosphorescent quantum efficiency in PLEDs was shown to arise mainly from triplet-triplet annihilation between dopants in the hosts with tert-butyl groups. It has been shown that in the devices with hosts without tert-butyl groups the efficiency roll-off is additionally affected by electric field quenching. In these carbazole based polymers, triplet dimers are formed and tert-butyl groups do not limit the intermolecular interactions to prevent triplet dimer formation, nevertheless tert-butyl groups reduce charge transport.