Visualizing a photosensitizer complex in action

Jul 18, 2012

A Japanese research group comprised of Dr. Tokushi Sato, Professor Shunsuke Nozawa, and Professor Shin-ichi Adachi of the Institute of Materials Structure Science at KEK, Professor Hiroshi Fujii of the Institute of Molecular Science at the National Institutes of Natural Sciences, and Professor Shin-ya Koshihara of the Tokyo Institute of Technology successfully visualized electron transfer process in a photosensitizer molecule, which is the fundamental process in solar cells and photocatalysts, at a temporal resolution of 100 ps.

Improvements of the efficiency and the lifetime of and photocatalysts are necessary to solve energy and environmental problems. Understanding the due to light irradiation, which is common to all these devices, is very important in realizing such developments. The photoexcitation mechanism in Ruthenium(II)-tris-2,2′-bipyridine [RuII(bpy)3]2+, used in solar cells, was observed in this research. The absorption band wavelengths (400–500 nm) for charge transfer from metal to ligand (MLCT) in this material are close to the maximum intensity wavelengths of the Sun, and therefore, efficient charge separation induced by solar light occurs in this material. Therefore, it is frequently used in investigating photochemical reactions.

The research group used time-resolved X-ray absorption spectroscopy at the Photon Factory at KEK to observe the changes in the electronic state and the molecular structure. The observation of the electronic state before and after irradiation showed that there is from ruthenium to bipyridine ligand within 100 ps, resulting in a change in the oxidation state of ruthenium from II to III. The bipyridine ligand moves toward the ruthenium atom by 0.04 Å with the charge transfer and a structurally distorted state exists in the photoexcited state .

This research elucidated the details of electron transfer, which is a fundamental process in solar cells and photocatalysts, and the change in molecular structure that accompanies electron transfer. This is important information in designing solar cells and , and it is expected to result in advances such as further improvements in device efficiency.

Explore further: Sweet-smelling breath to help diabetes diagnosis in children

More information: “Coordination and Electronic Structure of Ruthenium(II)-tris-2,2’-Bipyridine in the Triplet Metal-to-Ligand Charge Transfer Excited State Observed by Picosecond Time-Resolved Ru K-edge XAFS” The Journal of Physical Chemistry C, Vol. 116, No. 25 (June 28, 2012). doi:10.1021/jp3038285 . Authors:T. Sato, et al.

add to favorites email to friend print save as pdf

Related Stories

Working toward new energy with electrochemistry

Aug 20, 2007

In an effort to develop alternative energy sources such as fuel cells and solar fuel from “artificial” photosynthesis, scientists at the U.S. Department of Energy’s Brookhaven National Laboratory are taking a detailed ...

Electron transport in dye-based solar cells

May 30, 2012

European scientists studied electron flow in systems of organic photosensitive dyes and titanium-based materials. Results are particularly relevant to increasing the efficiency of a cost-effective class of ...

Dye-sensitized solar cells break a new record

Nov 14, 2011

(PhysOrg.com) -- Dye-sensitized Grätzel solar cells have just set a new efficiency benchmark. By changing the composition and color of the cells, an EPFL team has increased their efficiency to more than ...

Modeling How Electric Charges Move

Mar 13, 2008

Learning how to control the movement of electrons on the molecular and nanometer scales could help scientists devise small-scale circuits for many applications, including more efficient ways of storing and using solar energy. ...

Recommended for you

New material makes water and oil roll off

18 hours ago

Car finish, to which no dirt particles adhere, house fronts, from which graffiti paints roll off, and shoes that remain clean on muddy paths – the material "fluoropore" might make all this possible. Both ...

User comments : 0

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.