Single-Ion Transport Light-Emitting Electrochemical Cells: Designation and Analysis of the Fast Transient Light-Emitting Responses

A single-ion transport light-emitting electrochemical cell (SLEC) was designed. The SLEC is the first LEC-type device that can be driven by ac voltages indicating its fast response speed. The fast light-emitting response of the SLEC was attributed to the single-ion transport property of the device. Because of the easy migration of the cations under the influence of the external electric field, the electron injection from the cathode to the luminescent polymer (with low electronic affinity) was enhanced quickly. The experimental results demonstrate that compared with the ionic conductivity, the transport mode of the ionic species is a more sensitive factor that dictates the response speed of LECs. A color-shifting effect was also observed in the SLEC, the EL spectrum was greatly blue-shifted and expended (from orange to whitish). It possibly resulted from the interaction between naked and immobilized SO3- in the bulk of the polymer layer and the excitons in MEH−PPV.