A solid-state integrated photo-supercapacitor based on ZnO nanorod arrays decorated with Ag2S quantum dots as the photoanode and a PEDOT charge storage counter-electrode

Recent Advances in Photochargeable Integrated and All-in-One Supercapacitor Devices

Photoassisted energy storage systems, which enable both the conversion and storage of solar energy, have attracted attention in recent years. These systems, which started about 20 years ago with the individual production of dye-sensitized solar cells and capacitors and their integration, today allow more compact and cost-effective designs using dual-acting electrodes. Solar-assisted batterylike or hybrid supercapacitors have also shown promise with their high energy densities. This review summarizes all of these device designs and conveys the cutting-edge studies in this field. Besides, this review aims to emphasize the effects of point, extrinsic, intrinsic, and 2D-planar defects on the performance of photoassisted energy storage systems since it is known that defect structures, as well as electrical, optical, and surface properties, affect the device performance. Here, it is also targeted to draw attention to how critical the design, material selection, and material properties are for these new-generation energy conversion and storage devices, which have a high potential to see commercial examples quickly and to be recognized by more readers.

Progress of Photocapacitors

In response to the current trend of miniaturization of electronic devices and sensors, the complementary coupling of high-efficiency energy conversion and low-loss energy storage technologies has given rise to the development of photocapacitors (PCs), which combine energy conversion and storage in a single device. Photovoltaic systems integrated with supercapacitors offer unique light conversion and storage capabilities, resulting in improved overall efficiency over the past decade. Consequently, researchers have explored a wide range of device combinations, materials, and characterization techniques. This review provides a comprehensive overview of photocapacitors, including their configurations, operating mechanisms, manufacturing techniques, and materials, with a focus on emerging applications in small wireless devices, Internet of Things (IoT), and Internet of Everything (IoE). Furthermore, we highlight the importance of cutting-edge materials such as metal-organic frameworks (MOFs) and organic materials for supercapacitors, as well as novel materials in photovoltaics, in advancing PCs for a carbon-free, sustainable society. We also evaluate the potential development, prospects, and application scenarios of this emerging area of research.

Photo-supercapacitors based on nanoscaled ZnO

In this study, zinc oxide (ZnO) powders in two different morphologies, nanowire (NW) and nanoflower (NF), have been synthesized by the hydrothermal method. The eligibility of the pristine ZnO nanopowders as a photo-active material has been revealed by designing P-SC devices via the facile drop-casting method on both glass and plastic substrates in large-area applications. The impact of physical properties and especially defect structures on photo-supercapacitor (P-SC) performance have been explored. Although the dark Coulombic efficiency (CE%) of both NW and NF-based P-SC were very close to each other, the CE% of NW P-SC increased 3 times, while the CE% of NF P-SC increased 1.7 times under the UV-light. This is because the charge carriers produced under light excitation, extend the discharge time, and as confirmed by electron paramagnetic resonance, photoluminescence, and transmission electron microscopy analyses, the performance of P-SCs made from NF powders was relatively low compared to those produced from NW due to the high core defects in NF powders. The energy density of 78.1 mWh kg⁻¹ obtained for NF-based P-SCs is very promising, and the capacitance retention value of almost 100% for 3000 cycles showed that the P-SCs produced from these materials were entirely stable. Compared to the literature, the P-SCs we propose in this study are essential for new generation energy storage systems, thanks to their ease of design, adaptability to mass production for large-area applications, and their ability to store more energy under illumination.

Enhanced UV Photoresponsivity of ZnO Nanorods Decorated with Ag2S/ZnS Nanoparticles by Successive Ionic Layer Adsorption and Reaction Method

Recently, different kinds of energy band structures have been utilized to improve the photoelectric properties of zinc oxide (ZnO). In this work, ZnO nanorods were prepared by the hydrothermal method and then decorated with silver sulfide (Ag2S)/zinc sulfide (ZnS) via two-step successive ionic layer adsorption and reaction method. The photoelectric properties of nanocomposites are investigated. The results show that ZnO decorated with Ag2S/ZnS can improve the photocurrent of photodetectors from 0.34 to 0.56 A at bias of 9 V. With the immersion time increasing from 15 to 60 minutes, the photocurrent of photodetectors increases by 0.22 A. The holes in the valence band of ZnO can be transferred to the valence band of ZnS and Ag2S, which promotes the separation and suppresses the recombination of hole-electron pairs generated in ZnO. Moreover, electrons excited by ultraviolet (UV) light in Ag2S can also be injected into the conduction band of ZnO, which causes the photocurrent to increase more than the ZnO photodetector.