A droplet-based electricity generator with high instantaneous power density, high efficiency, and reliable long-term stability

Abstract

Droplet-based electricity generators (DEGs) have recently revolutionized the prospects for energy harvesting from raindrops. However, achieving high instantaneous power density, high efficiency, and reliable long-term stability remains challenging. Here, we propose a DEG with an intermediate metal electrode underneath the dielectric layer (IM-DEG) for substantial instantaneous outputs, high efficiency, and improved long-term stability. This intermediate metal layer not only plays a vital role as additional charge storage but also opens up a new route to inject negative charges into the dielectric layer from below to further increase the surface charge density. Unlike other ion injection techniques that inject negative charges from the top of the dielectric materials, in our case, the negative charges injected from below tend to remain in the dielectric layer without leaking to the upper electrode or droplets, resulting in elevated electrical performance and improved long-term stability. The IM-DEG's instantaneous peak voltage, power density, and energy conversion efficiency reach 836 V, 6.92 kW/m2, and 32.69%, respectively, while the instantaneous peak voltage drops less than 3% after 1000 h of a continuous flow of droplets. This method offers substantial electrical outputs with high efficiency and reliable long-term stability, paving the way for the future of raindrop energy harvesting.