Exciton-polaron interactions in polyfluorene films with β phase
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.
Citation
Montilla , F , Ruseckas , A & Samuel , I D W 2018 , ' Exciton-polaron interactions in polyfluorene films with β phase ' , Journal of Physical Chemistry C , vol. 122 , no. 18 , pp. 9766-9772 . https://doi.org/10.1021/acs.jpcc.8b01300
Publication
Journal of Physical Chemistry C
Status
Peer reviewed
ISSN
1932-7447Type
Journal article
Description
The authors acknowledge financial support from the European Research Council (grant 321305), Spanish Ministry of Economy Explora Ciencia Project MAT2013-49534-EXP and the Engineering and Physical Sciences Research Council (grants EP/L017008/1 and EP/J009016/1). I.D.W.S. also acknowledges support from a Royal Society Wolfson Research Merit Award.Collections
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