Planar Polymer Light-Emitting Electrochemical Cells with Ring-Shaped Bipolar Electrodes

Abstract

Polymer light-emitting electrochemical cells are demonstrated with circular driving electrodes and ring-shaped bipolar electrodes. The microfabricated electrode patterns enable the formation of seven to forty-nine concentric light-emitting rings across a large gap between the circular driving electrodes. Cells with BPEs exhibit vastly faster cell activation and much greater peak cell current. Cell activation in a PLEC constitutes in situ electrochemical doping and the formation of a light-emitting p–n junction. After junction formation, the PLEC can be discharged to produce an open-circuit voltage (V_OC). Herein, we demonstrate that the discharging open-circuit voltage is directly proportional to the number of BPEs introduced and the number of junctions formed. A 49-junction cell exhibits a record-high discharging V_OC of 98.5 V. Moreover, the activated cells can be frozen and operated as photovoltaic cells when exposed to light. Once again, a linear relation is observed between the photovoltaic V_OC and the number of activated junctions. The 49-junction cell exhibits a photovoltaic V_OC of 47.5 V, which increases to 64 V after partial dedoping to remove microshorts. These record-high V_OCs are contributed by the multiple p–n junctions formed in series across the BPEs. This study showcases the versatility of polymer light-emitting electrochemical cells in both device configurations and functionalities. The planar cell electrode pattern is highly scalable. This device configuration offers potential for an all-in-one device that can generate, store, and output electrical energy with variable voltage, eliminating the need for additional wiring.