Molecular Switches: Optoelectronic components based on a dye-sensitized TiO2 solar cell

April 24, 2006

Electronic components must continue to get smaller: Miniaturization has now reached the nanometer scale (10-9 m). In this tiny world, classic semiconductor technology is reaching its limits. We now need switches and other devices whose dimensions are on the scale of individual molecules. The difficulty with this is in the addressability and compatibility of molecular systems with the available nanoelectronic components. Until now, all molecular systems require at least one step in which a solution must be injected into the system and then rinsed out again, which is time-consuming.

L. Furtado, K. Araki, H. E. Toma, and co-workers at the University of São Paulo in Brazil describe for the first time an optoelectronic molecular gate that directly absorbs light and gives off electrical impulses.

The gate consists of a glass electrode onto which a thin, nanocrystalline film of TiO2 is deposited. A dye, in this case a cluster of three ruthenium–pyrazinecarboxylate complexes, is adsorbed to this surface. A platinum counter electrode is used, and the space between the electrodes is filled by an electrolyte solution of I3-/I2 in CH3CN.

When this gate is irradiated with light, electrons are excited, which leads to charge separation and a flow of current. The direction of the current changes depending on the wavelength of the light irradiating the system: at 350 nm, the electrons flow from the Pt electrode to the glass electrode; at 420 nm, they flow the other way.

At 350 nm, the TiO2 layer absorbs the light and gives off electrons to the underlying glass electrode. To compensate, the corresponding number of electrons is removed from the ruthenium cluster, which replaces them with electrons from the Pt electrode. At 420 nm, however, the ruthenium complexes are induced to give off electrons to the Pt electrode, which are re-supplied from the TiO2 layer.

The result is a switch that is not only turned on and off by light, but whose signal can change direction on the basis of the wavelength of light used.

Citation: Angewandte Chemie International Edition 2006, 45, No. 19, 3143–3146, doi: 10.1002/anie.200600076

Source: Angewandte Chemie

Explore further: Transparent lithium-ion battery that recharges via the sun demonstrated

Related Stories

MouthLab: Patients' vital signs are just a breath away

August 24, 2015

Engineers and physicians at the Johns Hopkins University School of Medicine have developed a hand-held, battery-powered device that quickly picks up vital signs from a patient's lips and fingertip. Updated versions of the ...

Recommended for you

For 2-D boron, it's all about that base

September 2, 2015

Rice University scientists have theoretically determined that the properties of atom-thick sheets of boron depend on where those atoms land.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.