American Institute of Physics, Applied Physics Letters, 4(96), p. 043308
DOI: 10.1063/1.3279155
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We report the use of blends composed of poly(9,9'-dioctylfluorene-alt-benzothiadiazole), F8BT, and a polymeric ionic liquid (PIL), poly(vinyl-ethylimidazolium bistrifluoromethanesulfonimide), as the active layer in light-emitting electrochemical cells (LECs) with the simple indium-tin-oxide/active-layer/Al configuration. The PIL provides both the ionic charge and the transport channel necessary for the devices to operate as LECs resulting in reduction of charge injection barriers at the electrode/active-layer interfaces. We find that the performance of devices using PIL:F8BT blends improved with respect to pure F8BT with maximum luminance increasing from 10-20 cd/m2 for pure F8BT to 2000-4000 cd/m2 for blends. Turn-on voltages were also reduced from above 7 V down to around 3.6-4 V. The maximum external quantum efficiency was increased from 10-3%-10-4% to values higher than 0.1%.