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Exploiting a Dual‐Fluorescence Process in Fluorene–Dibenzothiophene‐ S , S ‐dioxideCo‐Polymers to Give Efficient Single Polymer LEDs with Broadened Emission
Author(s) -
King Simon M.,
Perepichka Irene I.,
Perepichka Igor F.,
Dias Fernando B.,
Bryce Martin R.,
Monkman Andrew P.
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200801237
Subject(s) - materials science , fluorene , polymer , fluorescence , excited state , polymerization , light emitting diode , photochemistry , electroluminescence , indium tin oxide , monomer , optoelectronics , nanotechnology , atomic physics , optics , thin film , physics , chemistry , composite material , layer (electronics)
A description of the synthesis of random (9,9‐dioctylfluorene‐2,7‐diyl)–(dibenzothiophene‐ S , S ‐dioxide‐3,7‐diyl) co‐polymers (p(F‐S)x) by palladium‐catalyzed Suzuki cross‐coupling polymerization where the feed ratio of the latter is varied from 2 to 30 mol % (i.e., x = 2–30) is given. Polymer light emitting devices are fabricated with the configuration indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonic acid)/p(F–S)x/Ba/Al. The device external quantum efficiency increased as the ratio of the S co‐monomer was increased, up to a maximum of 1.3% at 100 mA cm −2 for p(F‐S)30 and a brightness of 3 770 cd m −2 (at 10 V). The S units impart improved electron injection, more balanced mobilities, and markedly improved device performance compared to poly(9,9‐dioctylfluorene) under similar conditions. These co‐polymers display broad emission, observed as greenish‐white light, which arises from dual fluorescence, viz. both local excited states and charge transfer states. Utilizing dual emission can reduce problems associated with Förster energy transfer from high‐energy to‐low energy excited states.