Enhancing water droplet-based electricity generator by harnessing multiple-dielectric layers structure

Harvesting water energy is promising to relieve the global energy crisis and reach the aim of carbon neutrality. However, few effective technologies can make use of water droplets as a power source efficiently. The droplet-based electricity generator (DEG) with a transistor-inspired design has resulted in enhanced energy harvesting efficiency by orders of magnitude over traditional designs. Despite this, the current DEG generally features a single dielectric layer, limiting its integration with other common objects to achieve "unnoticed" energy harvesting. In this work, we report a novel design featuring multiple dielectric layers-based DEG (M-DEG) that leverages other materials, such as household glass or umbrellas, as the second dielectric layer under the surface triboelectric layer to harvest water droplet energy without interfering with the original function of both. We find that the second dielectric layer enhances the output of M-DEG because of higher equivalent capacitance and charge density. The open circuit voltage and short-circuit current are increased by 90.6% and 68.7%, respectively. The maximal short-circuit current reaches up to record-breaking 17.9 mA. Moreover, a capacitor model for M-DEG is established, which well reveals the influence of the properties of dielectric layers and droplets on the electric output, and accurately predicts the results.