Evolution From Single to Hybrid Nanogenerator: A Contemporary Review on Multimode Energy Harvesting for Self-Powered Electronics

Energy harvesting devices have strong potential to not only meet growing global energy demand but also support a wide range of self-powered electronics applications. Solar cells, electrochemical cells, piezoelectric/triboelectric/pyroelectric nanogenerators, and magnetoelectric energy harvesters are enabling technologies for converting solar, chemical, mechanical, thermal, and magnetic energy to electricity. Merging these harvesters to form hybrid energy cells can help optimize operation of self-powered systems, providing multimode energy harvesting capability that can leverage several energy sources either simultaneously or individually. Energy produced from these hybrid energy cells even can be stored in Li-ion batteries to power various personal electronics, sensors, and next generation technology for the Internet of Things. Ultimately, hybridization provides another degree of freedom in terms of more effective energy utility. This review presents the evolution of the hybrid energy cell concept and development, explores the fabrication approaches taken, and provides insights on the limitations of existing devices, steps toward performance optimization, and the enormous potential for these technologies to benefit myriad applications. Hybrid energy cells show higher output performance by providing better charging characteristics than individual energy harvester unit.