Sputtered iridium oxide film (SIROF) for on-chip microsupercapacitors with integrated solar charging

Journal article, 2026

AbstractThe rapid development of microsupercapacitors (MSCs) has increased demand for high-performance electrode materials that can provide long-lasting energy storage with high power and energy densities. Sputtered iridium oxide film (SIROF) is a promising option due to its superior pseudocapacitive behavior, scalability, and compatibility with microfabrication techniques. In this work, we have explored sputtered iridium oxide films (SIROF) with a platelet morphology as electrode materials for on-chip microsupercapacitors. The electrochemical performance of the devices is systematically evaluated in a variety of electrolytes including acidic, neutral, alkaline, gel, and ionic liquid systems. Among aqueous electrolytes phosphoric acid (H3PO4) delivers the highest areal capacitance of 48.6 mF cm−2. The PVA/H3PO4 gel electrolyte provides enhanced cycling stability, retaining 99.5% of its capacitance after 10,000 cycles and exhibits reduced self-discharge. The ionic liquid EMIM TFSI enables higher energy and power densities through an extended operating voltage window and stable operation at elevated temperature of 60 °C. These findings provide valuable insights into the impact of electrode/electrolyte interaction on the overall performance of SIROF. Additionally, the MSCs demonstrate scalable operation and can be efficiently charged using commercial photovoltaic cells, highlighting their potential for integration into self-powered microelectronic systems. These results highlight the versatility of SIROF electrodes and their suitability for next-generation micro-energy storage applications.