Bilayer Boost to UV Assisted Supercapacitors: Enhanced Performance with Transparent TiO2/MoO3 Heterojunction Electrode

Abstract

Photo-assisted supercapacitor is a promising smart device component for achieving both energy conversion and storage. The photo-assisted functionality in a supercapacitor is realized through the choice of photo responsive electrode material under suitable illumination conditions. The well-known electrochemically active electrode materials are wide band gap semiconductors which absorb strongly in UV light. However, most of the prior studies on photo-assisted supercapacitors used visible light. Herein, we present a transparent TiO₂/MoO₃ bi-layer heterojunction made by simple solution process as an efficient electrode for photo-assisted supercapacitors under UV light illumination. The electrochemical performance of the electrode is significantly enhanced even with a less intense (0.05 mW/cm²) UV light, compared to dark as well as the single layer electrode under same illumination condition. The highest areal capacitance of 63.25 mF/cm² at 0.1 mA/cm² is achieved, that surpasses most of the recent relevant reports. The synergetic effect of UV illumination and the built-in potential at the type II heterojunction interface encourages ion insertion and better collection of the photo-generated carriers. The unique bi-layer design also leads to better rate capability features. Thus, the work presents a new prospect for the development of transparent energy storage devices to be used in future smart technologies.