Fabrication of all-solid-state electrochemical microcapacitors

All-solid-state electrochemical microcapacitors are fabricated using photolithography, electrochemical polymerization and solution casting techniques. Gold microelectrode arrays are fabricated by ultraviolet photolithography and a wet-etching method. Conducting polymers such as polypyrrole (PPy) are potentiostatically synthesized on these microelectrodes. A microcapacitor is made up of 50 parallel-connected pairs of microelectrodes. The width of the microelectrodes and the distance between them are each 50 μm. Two types of polymer electrolytes are applied, defined by the polymer matrix and ion-conducting media. Cell capacitance can be controlled by the total synthesis charge of the conducting polymers and a cell potential of 0.6 V is obtained. The electrochemical performance and charging–discharging mechanisms of all-solid-state microcapacitors are studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and constant-current discharge and the results are compared with those of microcapacitors with liquid electrolyte.