Transparent conducting oxide- and Pt-free flexible photo-rechargeable electric energy storage systems

Abstract

A highly flexible, transparent conducting oxide- and Pt-free photo-rechargeable electric energy storage system is demonstrated by integrating a dye-sensitized solar cell and a supercapacitor face-to-face on double-sided uniformly aligned TiO₂ nanotube arrays. The energy harvesting part consists of TiO₂ nanotubes as the photoanode and CuS networks as the counter electrode, yielding a PCE of 7.73%. Herein, CuS networks exhibited remarkable mechanical flexibility, superior transparency and excellent electronic conductivity, which not only served as conducting films but also as catalysts for dye-sensitized solar cells. The flexible all-solid-state supercapacitors are composed of polyaniline polymerized on TiO₂ nanotubes and carbon cloth, which act as the negative and positive electrodes, respectively. The self-powered photo-rechargeable device can be charged to 0.64 V in ∼30 s under standard AM 1.5 (100 mW cm⁻²) illumination conditions. In particular, the photo-charge and discharge performance remained almost stable under bending tests, which is crucial for applications in wearable and portable electronics.