A three-electrode integrated photo-supercapacitor utilizing graphene-based intermediate bifunctional electrode

Heterogeneous Structures Consisting of Rod-like ZnO Interspersed with Ce2S3 Nanoparticles for Photo-Sensitive Supercapacitors with Enhanced Capacitive Performance

Photosensitive supercapacitors incorporate light-sensitive materials on capacitive electrodes, enabling solar energy conversion and storage in one device. In this study, heterogeneous structures of rod-shaped ZnO decorated with Ce2S3 nanoparticles on nickel foam (ZnO@Ce2S3/NF) are synthesized using a two-step hydrothermal method as photosensitive supercapacitor electrodes for capacitance enhancement under visible light. The formation of ZnO@Ce2S3 heterogeneous structures is confirmed using various structural characterization techniques. The area-specific capacitance of the ZnO@Ce2S3/NF composite electrode increased from 1738.1 to 1844.0 mF cm-2 after illumination under a current density of 5 mA cm-2, which is 2.4 and 2.8 times higher than that of ZnO and Ce2S3 electrodes under similar conditions, respectively, indicating the remarkable light-induced capacitance enhancement performance. The ZnO@Ce2S3/NF electrode also exhibits a higher photocurrent and photovoltage than the two single electrodes, demonstrating its excellent photosensitivity. The improved capacitance performance and photosensitivity under illumination are attributed to the well-constructed energy-level structure, which stimulates the flow of photogenerated electrons from the outer circuit and the involvement of photogenerated holes in the resulting surface-controlled capacitance. In addition, the assembled ZnO@Ce2S3/NF-based hybrid supercapacitor exhibits a great energy density of 145.0 mWh cm-2 under illumination. This study provides a novel strategy for the development of high-performance solar energy conversion/storage devices.

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.

Integrated Photovoltaic Charging and Energy Storage Systems: Mechanism, Optimization, and Future

As an emerging solar energy utilization technology, solar redox batteries (SPRBs) combine the superior advantages of photoelectrochemical (PEC) devices and redox batteries and are considered as alternative candidates for large-scale solar energy capture, conversion, and storage. In this review, a systematic summary from three aspects, including: dye sensitizers, PEC properties, and photoelectronic integrated systems, based on the characteristics of rechargeable batteries and the advantages of photovoltaic technology, is presented. The matching problem of high-performance dye sensitizers, strategies to improve the performance of photoelectrode PEC, and the working mechanism and structure design of multienergy photoelectronic integrated devices are mainly introduced and analyzed. In particular, the devices and improvement strategies of high-performance electrode materials are analyzed from the perspective of different photoelectronic integrated devices (liquid-based and solid-state-based). Finally, future perspectives are provided for further improving the performance of SPRBs. This work will open up new prospects for the development of high-efficiency photoelectronic integrated batteries.

Designing flexible, smart and self-sustainable supercapacitors for portable/wearable electronics: from conductive polymers

The rapid development of portable/wearable electronics proposes new demands for energy storage devices, which are flexibility, smart functions and long-time outdoor operation. Supercapacitors (SCs) show great potential in portable/wearable applications, and the recently developed flexible, smart and self-sustainable supercapacitors greatly meet the above demands. In these supercapacitors, conductive polymers (CPs) are widely applied due to their high flexibility, conductivity, pseudo-capacitance, smart characteristics and moderate preparation conditions. Herein, we'd like to introduce the CP-based flexible, smart and self-sustainable supercapacitors for portable/wearable electronics. This review first summarizes the flexible SCs based on CPs and their composites with carbon materials and metal compounds. The smart supercapacitors, i.e., electrochromic, electrochemical actuated, stretchable, self-healing and stimuli-sensitive ones, are then presented. The self-sustainable SCs which integrate SC units with energy-harvesting units in one compact configuration are also introduced. The last section highlights some current challenges and future perspectives of this thriving field.

A poly(3,4-propylenedioxythiophene)/carbon micro-sphere-bismuth nanoflake composite and multifunctional Co-doped graphene for a benchmark photo-supercapacitor

Efficient storage of sunlight in the form of charge is accomplished by designing and implementing a photo-supercapacitor (PSC) with a novel, cost-effective architecture. Sulfur (S)- and nitrogen (N)-doped graphene particles (SNGPs) are incorporated in a TiO2/CdS photoanode. The beneficial effects of SNGPs such as the high electrical conductance promoting fast electron transfer to TiO2, a suitably positioned conduction band that maximizes charge separation, and its' ability to absorb red photons translate into a power conversion efficiency of 9.4%, for the champion cell. A new composite of poly(3,4-propylenedioxythiophene)/carbon micro-sphere-bismuth nanoflakes (PProDOT/CMS-BiNF) is integrated with the photoanode to yield the PSC. The photocurrent produced under 1 sun irradiance is directed to the supercapacitor, wherein, the synergy between the faradaic and electrical double layer charge accumulation mechanisms of PProDOT and CMS-BiNF bestows storage parameters of an areal capacitance of 104.6 mF cm-2, and energy and power densities of 9 μW h cm-2 and 0.026 mW cm-2. An overall photo-conversion and storage efficiency of 6.8% and an energy storage efficiency of 72% exhibited by the PSC are much superior to those delivered by a majority of the PSCs reported in the literature on the otherwise highly efficient perovskite solar cell or the expensive Ru dye based solar cells.

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

A planar solid-state photocapacitor with two electrodes has been prepared for the first time using a passivated film of ZnS with Ag2S quantum dots deposited on ZnO nanorods, which were electrochemically grown on ZnO seed layers, as the photoanode. The supercapacitor part is composed of a electrodeposited poly(3,4-ethylene-dioxythiophene) PEDOT film as the counter-electrode and an ionic liquid-based electrolyte between them deposited by the dip coating method. The different nanostructures and electrodes were morphologically and structurally characterized, and the device was electrochemically characterized and could reach a potential of 0.33 V during photocharge and a storage efficiency of 6.83%.

Bifunctional Photo-Supercapacitor with a New Architecture Converts and Stores Solar Energy as Charge

Photo-supercapacitors (PSCs) combine functions of energy harvesting and storage in a single device, and in this study, a new architecture for a PSC is designed and implemented. Cadmium sulfide (CdS) quantum dots/hibiscus (hb) dye co-sensitized TiO₂ is used as the solar cell. Poly(3,4-ethylenedioxypyrrole) (PEDOP)@manganese dioxide (MnO₂) is employed as the counter electrode (CE) for the solar cell and also as the electrodes for the symmetric supercapacitor. The two ends of a long flat current collector support two spatially separated PEDOP@MnO₂ coatings, which serve as the CEs for the TiO₂/hb/CdS photoanode and yet another PEDOP@MnO₂ electrode in sandwich configurations. In this cell, under 1 sun (100 mW cm^-2) illumination, the TiO₂/hb/CdS photoanode undergoes charge separation and by channeling the photocurrent to the PEDOP@MnO₂ electrodes, the symmetric cell part is charged to a voltage of 0.72 V. The PSC delivers a specific capacitance of 183 F g^-1, an energy density of 13.2 Wh kg^-1, and a power density of 360 W kg^-1 at a discharge current density of 1 A g^-1. During the self-discharge process, PEDOP@MnO₂-based PSC retains a voltage of 0.72 V up to 500 s and maintains a stable voltage of 0.5 V thereafter. The TiO₂/hb/CdS photoanode with the PEDOP@MnO₂ CE in an aqueous polysulfide-silica gel electrolyte delivers a power conversion efficiency of 6.11%. This demonstration of a novel PSC opens up opportunities to develop new architectures for efficiently combining energy conversion and storage.

A new concept of a transparent photocapacitor

This work presents a new concept of a transparent solid-state photocapacitor which exhibits high transmittance compared to other reported results, and an acceptable specific capacitance.