High performance quasi-solid-state photo-supercapacitor based on zinc oxide nanostructured electrodes with various morphologies

The development of photosupercapacitors for solar energy collection and storage is one of the most promising areas to power future technologies. In this study, we report the effects of three different morphologies of nanorods (NR), nanoflowers (NF), and nanosheets (NS) on the performance of zinc oxide (ZnO) semi-solid-state photosupercapacitors (QSS-PSCs). Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) measurements of QSS-PSCs under dark and AM1.5 conditions demonstrate that the morphology affects the charging time and, consequently, the specific capacitance (Cp) of the QSS-PSC. Among the ZnO:NR, ZnO:NF, and ZnO:NS PSCs, the highest surface area, charging time, and Cp were obtained with ZnO:NS-based devices. The ZnO:NSbased QSS-PSC demonstrated a fourfold improvement, increasing Cp from 586 Fg- 1 in the dark to 2348 Fg- 1 in the light at a scan rate of 1 mVs- 1. Furthermore, the ZnO:NS QSS-PSC devices demonstrated high cycle stability, completing 16,000 cycles with 93 % Coulombic efficiency (%CE). This study demonstrated that ZnO nanostructures offer high potential for electrochemical energy storage devices that can be charged directly by sunlight through appropriate morphology selection and device design.