Coating materials

This article presents a brief overview of the recent advancements in rectenna devices (optical rectenna) designed to operate over a high-frequency radiation range, i.e., terahertz (THz), infrared (IR), and visible light frequencies. Since the discovery of microwave transmission and radio wave energy harvesting capabilities of rectennas, they have been considered a potential candidate for energy harvesting. Unlike other current commercial energy conversion technologies such as solar and thermal cells, whose operation is limited to a narrow range within the electromagnetic spectrum, rectennas have no theoretical limitations; they can operate over a broad range in the electromagnetic spectrum. However, in the high-frequency radiation range (THz, IR, and visible light), the rectenna devices developed to date are rendered nonfunctional exhibiting a significantly lower efficiency than RF rectennas. Various aspects of rectenna technology are being extensively researched in several labs worldwide for determining prospective solutions. It has been proposed that a high-frequency radiation rectenna can be realized by downsizing the antenna to the nanoscale and integrating a nanodiode operating in that high-frequency range. This review first briefly describes the operation principle of rectenna and the challenges in high-frequency-radiation rectification. Then, it discusses important points regarding the research progress of rectenna components (antenna and diode) for THz, IR, and visible light frequencies, with a special focus on organic molecules as an efficient building block for diodes operating in the high-frequency radiation range. Finally, the proposed models and the most common rectenna design approaches are summarized with a final conclusion.