Molecular Photoelectric Switch Using a Mixed SAM of Organic [60]Fullerene and [70]Fullerene Doped with a Single Iron Atom

We describe a photoswitch fabricated on indium tin oxide (ITO) as a self-assembled monolayer (SAM) of two fullerene molecules, a purely organic [60]fullerene that generates an anodic current and a [70]fullerene doped with a single iron atom. This device generates a bidirectional photocurrent upon irradiation at 340 and 490 nm. The new [70]fullerene iron complex bearing three rigid carboxylic acid legs, Fe[C(70)(C(6)H(4)C(6)H(4)COOH)(3)]Cp, generates only a cathodic current upon photoexcitation between 350 and 700 nm, whereas the organic [60]fullerene absorbs at wavelengths shorter than 500 nm. The quantum efficiency of the photocurrent generation by the mixed SAM is comparable to that of a single-component SAM, indicating that the individual diode molecules on ITO generate photocurrents independently with little cross talk.