Correlation Between Triplet–Triplet Annihilation and Electroluminescence Efficiency in Doped Fluorescent Organic Light-Emitting Devices

Authors

  • Yichun Luo,

    Corresponding author
    1. Department of Electrical and Computer Engineering University of Waterloo 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada)
    • Department of Electrical and Computer Engineering University of Waterloo 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada).
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  • Hany Aziz

    1. Department of Electrical and Computer Engineering University of Waterloo 200 University Avenue West, Waterloo, Ontario, N2L 3G1 (Canada)
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Abstract

Triplet–triplet annihilation (TTA) is studied in a wide range of fluorescent host:guest emitter systems used in organic light-emitting devices (OLEDs). Strong TTA is observed in host:guest systems in which the dopant has a limited charge-trapping capability. On the other hand, systems in which the dopant can efficiently trap charges show insignificant TTA, an effect that is due, in part, to the efficient quenching of triplet excitons by the trapped charges. Fluorescent host:guest systems with the strongest TTA are found to give the highest OLED electroluminescence efficiency, a phenomenon attributed to the role of TTA in converting triplet excitons into additional singlet excitons, thus appreciably contributing to the light output of OLEDs. The results shed light on and give direct evidence for the phenomena behind the recently reported very high efficiencies attainable in fluorescent host:guest OLEDs with quantum efficiencies exceeding the classical 25% theoretical limit.

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