Exciton-polaron interactions in polyfluorene films with β phase
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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.
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
Journal of Physical Chemistry C
© 2018, American Chemical Society. This work has been made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1021/acs.jpcc.8b01300
DescriptionThe 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.
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