Photo-chargeable supercapacitors are attracting significant research interest as promising alternative to energy storage devices suitable for next-generation smart appliances. In this work, a heterojunction of cadmium sulphide (CdS) nanoparticles and zinc oxide (ZnO) nanorods is obtained for designing a broadband photo responsive symmetrical supercapacitor. Ultraviolet (UV) absorption by ZnO and visible light interaction with the CdS nanoparticles in the heterostructure contribute synergistically to deliver UV to visible broad spectral response. The heterojunction formation is confirmed by field effect scanning electron microscopy and high-resolution transmission electron microscopy with elemental mapping. Areal capacitance was measured in both the dark and under illumination conditions using cyclic voltammetry and galvanostatic charge–discharge, supported by impedance spectroscopy. Enhancement of areal capacitance from the dark condition was observed between ~238% to ~1264% for different illumination in broad spectral range measured from the cyclic voltammetry measurements at a constant scan rate of 50 mV/s and achieved a highest capacitance value of ~139 μF /cm^2 under 475 nm visible light for the scan rate of 10 mV/s. Moreover, the charge generation and storage mechanism under illumination were verified by phototransient response and open-circuit potential measurements. The excellent electrochemical performance observed by maintaining high efficiency (~94.7%) with improved cyclic stability upto 5000 cycles. A good capacitance retention (~90%) in bending mode when heterojunction applied in bendable devices provide broad future prospect for the metal oxide-sulphide interface in photo-chargeable smart devices.
A novel heterostructure prepared by coating of CdS nanoparticles on chemically grown ZnO NRs on FTO coated glass substrate and also on transparent flexible substrate, ITO-PET to utilise in photo-chargeable symmetrical liquid electrolyte based flexible supercapacitor. Using synergistic effect of UV absorption by ZnO and visible response by CdS, the heterostructure under UV to visible broad spectrum generates electron hole pairs followed by separation under built-in potential at the interface of ZnO and CdS. The symmetric supercapacitor made by this heterostructure under illumination convert light energy into electrochemical energy with exceptional enhancement in areal capacitance from its dark value ranges between ~238% to ~1264% under broad spectral range (λ~365–520 nm) evaluated from CV curve at a constant value of 50 mV/s.
The details can be found here on https://doi.org/10.1016/j.electacta.2023.143507 .
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