Phys. Rev. Lett. 98, 197402 (2007) [4 pages]Single-Step Triplet-Triplet Annihilation: An Intrinsic Limit for the High Brightness Efficiency of Phosphorescent Organic Light Emitting DiodesReceived 8 October 2006; published 10 May 2007 We investigate triplet-triplet annihilation in molecular host-guest systems where triplets are localized on spatially separated guest molecules. Our results indicate that the dominant mechanism of annihilation is single-step long-range (Förster-type) energy transfer between two excited guests. This mechanism leads to a fundamental limit for the efficiency of phosphorescent organic light emitting diodes at high luminance. Our model is confirmed by photoluminescence decay experiments on 2,3,7,8,12,13,17,18-octaethylporphine platinum as guest in a host matrix of 4,4′-N,N′-dicarbazole-biphenyl. © 2007 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.98.197402
DOI:
10.1103/PhysRevLett.98.197402
PACS:
78.55.Kz, 78.20.−e, 78.60.Fi, 78.66.Qn
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