An optically transparent rectifying metasurface for 2.4/5.8 GHz dual-band RF energy harvesting

In this paper, an optically transparent rectifying metasurface system (RMS) is designed and validated for simultaneously harvesting radio frequency (RF) energy while enabling the efficient transmission of visible light. The RMS comprises an optically transparent metasurface absorber (OTMA) based on indium tin oxide materials and a voltage-doubling rectifier circuit. The proposed RMS features several advantages, including polarization insensitivity, wide incidence angle coverage, low profile, and the ability to operate at low incident power densities. Utilizing a stacked structure, the RMS and the solar cell can provide a more hybrid output power to accommodate more application scenarios. To validate its performance, a prototype 3 x 3 OTMA array was designed, fabricated, and measured. Results demonstrate that the fabricated RMS achieves RF to DC efficiencies of 19.64% at 2.4 GHz and 7.92% at 5.8 GHz, with an impressive 80% optical transparency. Furthermore, solar energy harvesting tests show that the measured maximum power point for the RF/solar hybrid energy harvesting is 13.11% higher than that of a single solar panel under a light intensity of 257 lux.