Flexible and Wearable Hybrid RF and Solar Energy Harvesting System

In this article, we demonstrate a flexible and wearable hybrid radio frequency (RF) and solar energy harvesting system for powering wearable electronic devices. The system consists of a flexible transparent antenna, a flexible transparent rectifying circuit, and an amorphous silicon solar cell. By utilizing transparent stacked structure, the rectenna and the solar cell can provide more hybrid output power to accommodate more application scenarios. The flexible transparent antenna shows two impedance matching bandwidths of 3.5-3.578 and 4.79-5.09 GHz, covering n78/n79 fifth-generation (5G) communication frequency band and 5-GHz WiFi frequency band. At the frequency of 3.5 GHz, the flexible transparent rectifying circuit achieves a high RF-to-dc conversion efficiency of 54.67% at 13 dBm RF input power. In the room with a light intensity of 210 lux, compared with a single solar cell, the hybrid energy harvesting system can obtain an additional 35.6%-769.5% output power when the RF source power is varied from 4 to 10 dBm. These results demonstrate that the proposed flexible and wearable RF-solar energy harvester can provide reliable electric power supply, which can be a potential candidate for powering wearable electronic devices, distributed sensors and IOT devices.