Self-Assembly and Electrochemical Characterization of Ferrocene-based Molecular Diodes for Solar Rectenna Device

Bailey [1] proposed in 1972 that a nanoscale antenna coupled with a rectifier can harvest broad range electromagnetic radiation from visible to infrared. To incorporate this concept in practical systems, there were two main technological bottle necks that have to be overcome: Antenna miniaturization and rectification in terahertz frequency. With current technology and equipment [2], we are proposing a third-generation rectenna-based solar cells composed of Ag nanocubes to harvest ambient visible and infrared electromagnetic waves coupled to ferrocene-based molecular diodes [3] capable of switching at terahertz frequency to convert this received energy into DC power. The function of these molecular diodes is two-fold: They rectify and provide an uniform nano-cavity between silver top electrode and gold bottom electrode. These nano-cavities are capable to support gap plasmon modes and absorption of light in both narrow and broad range, depending on the nanocube size and dispersion. A self-assembled monolayer (SAM) of ferrocene alkane-dithiol is deposited in this nano-cavity making it possible to form molecular sized nano-gaps well below the usual 3 nm, and this structure is robust and reproducible [4]. This SAM can be deposited directly or via a two-step click chemistry on the surface to have along with control over the orientation of the molecule. By tuning the orientation and position of the ferrocene moiety, the direction of rectification can be controlled [3]. Hence, the SAM does not only act as a rectifier but also provides mechanical support combining photonic and electrical properties. This paper focuses on studying the electrical and supramolecular structure of these molecular diode based SAMs.