  Molecular-scale diodes made from self-assembled monolayers (SAMs) could
complement silicon-based technologies with smaller, cheaper, and more versatile
devices. However, advancement of this emerging technology is limited by
insufficient electronic performance exhibited by the molecular current
rectifiers. We overcome this barrier by exploiting the charge-transfer state
that results from co-assembling SAMs of molecules with strong electron donor
and acceptor termini. We obtain a substantial enhancement in current
rectification, which correlates with the degree of charge transfer, as
confirmed by several complementary techniques. These findings provide a
previously unexplored method for manipulating the properties of molecular
electronic devices by exploiting donor/acceptor interactions. They also serve
as a model test platform for the study of doping mechanisms in organic systems.
Our devices have the potential for fast widespread adoption due to their
low-cost processing and self-assembly onto silicon substrates, which could
allow seamless integration with current technologies.
