### Abstract: Ultraflexible Energy Harvesting-Storage System for Wearable Applications In a significant advancement for wearable technology, a team led by Professor Xu Xiaomin from Tsinghua University's Shenzhen International Graduate School, in collaboration with Professor Zhou Guangmin and others, has developed an ultraflexible energy harvesting and storage system (FEHSS). This innovative system, which is only 90 micrometers thick, integrates high-performance organic photovoltaic (OPV) components with ultra-thin zinc-ion batteries (ZIBs), demonstrating its potential as a next-generation green energy solution for wearable devices and everyday electronics. #### Key Components and Innovations 1. **Ultraflexible Organic Photovoltaic (OPV) Devices:** - The OPV devices utilize a PM6:O-IDTBR:Y6 ternary blend system, which broadens the light absorption range and enhances the exciton dissociation efficiency at the donor-acceptor interface. - The use of EDT (ethylenediaminetetraacetic acid) to passivate the ZnO electron transport layer significantly improves the device's photostability. - These optimizations result in a single OPV device achieving a high photoelectric conversion efficiency (PCE) of 16.18%, a lifespan exceeding 1500 hours in a dark inert environment, and maintaining over 92% of its initial PCE after 500 hours of continuous illumination at 50 mW cm-2 light intensity. 2. **High-Performance OPV Modules:** - The researchers designed OPV modules that can be adjusted for power output, achieving a PCE of 10.5% and a peak power output of over 68.9 mW for a module with an effective area of 6.72 cm2. - The module exhibits a power output density of 10.2 mW cm-2 and demonstrates excellent mechanical strength across various light intensities. 3. **Ultra-Thin Zinc-Ion Batteries (ZIBs):** - The ZIBs are composed of a zinc cathode, a manganese dioxide-graphite anode, and an ultra-thin hydrogel electrolyte. - A novel 10-micrometer thick polyvinyl alcohol-oxide graphene (PVA-GO) hydrogel was developed, offering superior mechanical compliance and compensating for minor capacity losses due to its ultra-thin nature. - The ultra-thin ZIBs have a total thickness of 85 micrometers and exhibit good rate performance and cycling stability. 4. **Integrated FEHSS:** - The FEHSS integrates the ultraflexible OPV modules, ultraflexible organic photodiodes (OPDs), and ultra-thin ZIBs. - The OPDs serve as rectifiers, preventing current from flowing back into the ZIBs. - The system, when configured with three ZIBs in series, can output a voltage of 5.4V and has an energy density higher than 5.82 mWh cm-2. - The FEHSS demonstrates stable efficiency, excellent mechanical flexibility, and robustness, outperforming similar systems in terms of overall performance. #### Applications and Impact - **Wearable Biomedical Sensors:** - The FEHSS can be seamlessly integrated into fabrics to power wearable biomedical sensors, such as those for ECG monitoring, which can transmit data in real-time to a smartphone, enhancing health management. - **Consumer Electronics:** - The system can charge smartphones and smartwatches without hindering user activities, providing a new and environmentally friendly outdoor power solution. #### Research Significance The development of this ultraflexible energy harvesting and storage system addresses critical challenges in the wearable electronics industry, including the need for high efficiency, durability, and continuous power output. By integrating these components into a single, lightweight, and flexible system, the research paves the way for more advanced and user-friendly wearable devices. The findings were published in *Nature Communications* under the title "An Ultraflexible Energy Harvesting-Storage System for Wearable Applications." #### Acknowledgments The research was supported by the National Natural Science Foundation of China, the Guangdong Provincial Natural Science Foundation, the Shenzhen Science and Technology Innovation Commission's Excellent Youth Basic Research Project, the Shenzhen University Key Discipline Stabilization Support Program, the Shenzhen High-Level Talent Team Project, and the Shenzhen Geim Graphene Center. The first author of the paper is Sakeena Saifi, a 2020 master's student at Tsinghua University's Shenzhen International Graduate School. The corresponding authors are Associate Professor Xu Xiaomin from Tsinghua University and Academician Cheng Huiming from the Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences. Other contributors include Associate Professor Zhou Guangmin, Professor Peter Müller-Buschbaum from Technical University of Munich, and doctoral students Xiao Xiao, Cheng Simin, and Guo Haotian from Tsinghua University's Shenzhen International Graduate School. #### Paper Link - [Nature Communications: An Ultraflexible Energy Harvesting-Storage System for Wearable Applications](https://www.nature.com/articles/s41467-024-50894-w) This groundbreaking work not only advances the field of flexible electronics but also promises to revolutionize the way we power and use wearable devices, making them more comfortable, efficient, and sustainable.