Ultrahigh‐Working‐Frequency Embedded Supercapacitors with 1T Phase MoSe2 Nanosheets for System‐in‐Package Application

Commercial aluminium electrolyte capacitors (AECs) are too large for integration in future highly integrated electronic systems. Supercapacitors, in comparison, possess a much higher capacitance per unit volume and can be embedded as passive capacitors to address such challenges in electronics scaling. However, the slow frequency response (<101 Hz) typical of supercapacitors is a major hurdle to their practical application. Here, it is demonstrated that 1T‐phase MoSe2 nanosheets obtained by laser‐induced phase transformation can be used as an electrode material in embedded micro‐supercapacitors. The metallic nature of MoSe2 nanosheet‐based electrodes provides excellent electron‐ and ion‐transport properties, which leads to an unprecedented high‐frequency response (up to 104 Hz) and cycle stability (up to 106 cycles) when integrated in supercapacitors, and their power density can be ten times higher than that of commercial AECs. Furthermore, fabrication processes of the present device are fully compatible with system‐in‐package device manufacturing to meet stringent specifications for the size of embedded components. The present research represents a critical step forward in in‐package and on‐chip applications of electrolytic capacitors.