Exciton-polaron interactions in polyfluorene films with β phase

Francisco Montilla, Arvydas Ruseckas, Ifor D. W. Samuel

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13 Citations (Scopus)
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Abstract

Fluorescence quenching by electric charges is an important loss mechanism in high-brightness organic light emitting diodes (OLEDs) but its effect is difficult to quantify in working devices. Here we combine an electrochemical technique to control the charge density with time-resolved photoluminescence to distinguish between different quenching mechanisms. The material studied was the blue electroluminescent polymer poly(9,9-dioctylfluorenene) with β phase. Our results show that quenching occurs by Förster resonance energy transfer and is mediated by exciton diffusion. We determine the quenching parameters over a wide range of charge concentrations and estimate their impact on the OLED efficiency roll-off at high current density. We find that fluorescence quenching by charges and singlet-triplet exciton annihilation are the two main mechanisms leading to the efficiency roll-off. Our results suggest that hole polarons are not very effective quenchers of singlet excitons which is important for understanding current devices and encouraging for the development of high-brightness OLEDs and lasers.
Original languageEnglish
Pages (from-to)9766-9772
JournalJournal of Physical Chemistry C
Volume122
Issue number18
Early online date12 Apr 2018
DOIs
Publication statusPublished - 10 May 2018

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