The growing demands for smaller, faster, yet less expensive and more versatile electronics, have led to a surge of efforts focused on the development of new componentry technologies. Molecular-scale devices could address this challenge and are being touted to become a core technology of the 21st century, complementing the conventional silicon-based industry with applications currently not possible. One of the simplest configurations is the molecular diode, which consists of a self-assembled monolayer (SAM) sandwiched between two electrodes and its function is to introduce an asymmetry between the current measured under positive and negative bias regimes, respectively. The efficiency of current rectification, quantified as the rectification ratio, is dependent on many factors, including the molecular structure of the SAM, its density and degree of order, as well as coupling to the electrodes. In this talk I will address these topics by discussing first the dependence of the rectification on the strength of the dipole moment of the molecules, followed by an example of manipulating the properties by exploiting the charge-transfer that results from co-assembling molecules with strong electron donor and acceptor termini.¹ We further show that the molecule/electron coupling resulting from the delocalization of electrons lone pairs controls the position of the molecular orbitals participating in transport, making it efficient for one bias polarity and inefficient for the opposite polarity. In the case of a strong coupling, this led to rectification ratios greater than 2500.² This performance was obtained in molecular diodes fabricated on silicon, which has a very low natural roughness, and thus require no additional processing. Our molecules are obtained from a simple, robust, and high-yield synthetic procedure and may yield hybrid systems when integrated with other more mature silicon technologies that are currently included in consumer electronics to expand its use toward novel functionalities governed by the molecular species grafted onto its surface. One example is that of a water sensor, which transduces the ambient moisture absorbed into the device through the porous electrode to electrical signal. By monitoring these changes, we demonstrate clear and reproducible changes in rectification ratio that are reversible upon multiple cycles.