Improving the performance of water droplet power generator by inserting an electron trapping layer into a fluoropolymer coated polyimide film

Droplet-based electricity generator (DEG) has been demonstrated as a feasible and promising method of energy harvesting from the environmental water, such as rain and tap water. However, the high material costs, the large usage of fluoropolymer and the low output power density are still challenges for DEGs to be used as the practical applications. In this study, we proposed a DEG of the three-layers structure composed of polyimide layer, tungsten trioxide (WO3), and an ultra-thin fluoropolymer layer was proposed. Then the effects of the multilayer structure of the DEG and the droplet parameters (type of droplet, volume, and falling height) on its performance was investigated through the measurements of surface potential and voltage waveform. By optimizing the parameters for micro-meter order thick polyimide, the performance of the DEG was significantly improved, and the voltage of 10 V orders, and a peak power of 2.7 mW was achieved by a 50 μl single water droplet, which was sufficient to light a small LED.