A New Figure of Merit for Solar Charging Systems: Case Study for Monolithically Integrated Photosupercapacitors Composed of a Large‐Area Organic Solar Cell and a Carbon Double‐Layer Capacitor

Abstract

The global trend toward automatization and miniaturization of smart devices has triggered the development of reliable off‐grid power sources with low economic and environmental impact. Such autonomy can be provided when a photovoltaic cell is integrated with an electrochemical double‐layer capacitor in one monolithic power pack. This work demonstrates a reliable and straightforward approach to monolithically integrate high‐performance organic solar cells with mesoporous nitrogen‐doped carbon nanosphere‐based supercapacitors in a single device with a three‐electrode configuration. To assess the efficiency of the device, a novel approach is presented that relies on the direct monitoring of both integrating parts during illuminated and dark phases and accounts for possible losses. The evaluation with the standard literature approach shows an outstanding performance of the integrated photosupercapacitor with a peak photoelectrochemical energy conversion efficiency of 17%. However, this type of efficiency does not properly represent the real overall efficiency of the device. Based on the newly developed efficiency calculation, a more modest overall cycle efficiency of 2% is obtained, which represents the overall performance of the integrated device in a better way. This versatile evaluation approach is applicable for all kinds of integrated multifunctional photoconversion–storage systems.

Early career scientists converse on the future of soft robotics

“…AVFs often use actuators that react to a change in temperature (SMAs, SMPs), humidity (hydrogels) or light (LCEs) with a closure of the trap lobes (Esser et al, 2020). Integration of energy harvesting structures like flexible solar cells (Pagliaro et al, 2008;Roldán-Carmona et al, 2014;Jung et al, 2019;Zimmermann and Würfel, 2020;Horii et al, 2022), solar batteries (Büttner et al, 2022) or solar supercapacitors (Berestok et al, 2021;Berestok et al, 2022;Delgado Andrés et al, 2022) might provide enough energy to supply sensors or low energy actuators in the future; for more details on energy harvesters, please look in Section 5. With such systems, autonomous bio-inspired or soft robots could be powered and outfitted to gather sensory data, e.g., in as small scale UAVs or drones (Han et al, 2009;Jafferis et al, 2019), or to interact with the users and environment as autonomous fully flexible healthcare robots or devices.…”

“…Next to system integration, the makeup of harvesters itself can be a challenge as for the use in soft robotics, they need to be lightweight, robust and ideally based on flexible materials. Usable systems in this case are flexible solar cells (Pagliaro et al, 2008;Roldán-Carmona et al, 2014;Jung et al, 2019;Zimmermann and Würfel, 2020;Horii et al, 2022), solar batteries (Büttner et al, 2022) or solar supercapacitors (Berestok et al, 2021;Berestok et al, 2022;Delgado Andrés et al, 2022) as well as triboelectric nanogenerators (TENGs) (Wu et al, 2019;Wang, 2020), piezoelectric nanogenerators (PENGs) (Lee et al, 2018), thermoelectric generators (TEGs) (Sherkat et al, 2022), biofuel cells or microbial fuel cell (MFC) Frontiers in Robotics and AI frontiersin.org (Ieropoulos et al, 2005;Kim et al, 2007;Tauber and Fitzgerald, 2021) and hybrids system, e.g., of TENG and biofuels cells (Liu et al, 2022). These can generate electricity to power low-energy consumers for autonomous wearable sensing and transmit sensory data to microprocessors and computers.…”

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

“…84 The 85 A monolithically integrated device of high-performance OPV with mesoporous nitrogen-doped carbon nanosphere-based SCs was constructed in a three-electrode configuration and resulted in 17% photoelectrochemical conversion efficiency. 81 Ti 3 C 2 T x -type MXene has been utilized as a transparent common electrode in a PSC device by integrating a flexible OPV to display a high volumetric capacitance (502 F cm −3 ) and a high power conversion efficiency of 13.6%. 86 Another PSC device fabricated using a dual-functional-layered graphene oxide (GO)-incorporated PEDOT:PSS as the common electrode exhibited ∼81% energy storage efficiency.…”

“…OPV devices grant benefits of being low cost, lightweight, and flexible among other PV devices. Thus, several studies have been reported on the basis of OPV-integrated PSC systems. − Shin et al reported an integrated PSC device utilizing the organic PV and solid-state SC in which both share an indium–tin-oxide (ITO) electrode for enhanced charge propagation (Figure a,b) . The overall energy conversion–storage efficiency of 2.27% was achieved when the device was charged under 1 sun illumination.…”

Organic photo-battery with high operating voltage using a multi-junction organic solar cell and an organic redox-polymer-based battery

“…However, most solar cells deployed in this regard are singlejunction cells and therefore usually have a limited voltage (o1 V). 14,15,18,25,26 Hence they are unable to charge most battery types, as higher voltages are required, and can only assist in the charging process (''photo-assisted charging''), thusrequiring an additional power supply. [27][28][29][30][31][32][33][34][35][36] While some systems have been reported that circumvent this limitation by using tandem or multi-junction solar cells, 16,37 the voltages are still insufficient in most cases, and batteries with a lower voltage (up to 1.6 V) must be selected, 16 thereby decreasing the energy density of the device.…”