Fabrication of interdigitated micro-supercapacitor devices by direct laser writing onto ultra-thin, flexible and free-standing graphite oxide films

In this work we present graphene-based in-plane flexible interdigitated micro-supercapacitor devices fabricated through direct laser writing onto ultra-thin graphite oxide (GO) films. The fabrication route is simple, fast, additive-free, mask-free and cost effective. This involves direct micro-writing of reduced graphene oxide (rGO) by a pulsed UV laser on a very small area (1.14 cm(2)). The fabricated micro-supercapacitor contains nineteen pairs of rGO electrodes separated by the unreduced portion of the GO film. The single laser patterned rGO electrode presents low resistivity, while the unpatterned portion is non-conducting. Under the optimized laser parameters the 2.2 mu m ultra-thin GO films were completely and uniformly reduced. The electrochemical measurements showed that the micro-supercapacitor, packed in a glass cavity, and in the presence of a liquid electrolyte have a capacitance nearly 288% higher (288.7 mF cm(-3)) compared to the as-fabricated device (0.36 mF cm(-3)). The as-fabricated micro-supercapacitor without electrolyte also shows some capacitance due to the presence of free ions in the unreduced portion of GO which plays a crucial role. Furthermore, the cycling stability of the as-fabricated micro-supercapacitor is robust, with not much performance degradation for more that 5000 cycles.