Capturing light in an efficient dye trap

May 10, 2013
Figure 1: The ABPX dye produces fluorescence in both solution (left) and aggregate state (right). Credit: 2013 Shinichiro Kamino, RIKEN Center for Life Science Technologies

Chemical compounds that can efficiently capture and convert light energy are in high demand as key components of inexpensive solar cells and advanced optical sensors. Carbon-based organic dyes are particularly strong candidates for such applications due to their low cost compared with the conventionally used silicon, but the lackluster performance of organic dyes has so far hindered their uptake by industry. Shuichi Enomoto, Shinichiro Kamino and colleagues at the RIKEN Center for Life Science Technologies have now discovered an organic dye that overcomes one of the major hurdles of this promising technology.

A wide range of are known to exist and their performance is limited by a tendency for the molecules to form aggregates that dissipate absorbed light energy. When an organic dye molecule absorbs a photon of light, it receives a kick of energy that can be put to use either by channeling the energy into an electric current in a solar cell, or re-emitting the light to indicate the presence of a , as part of an optical sensor. The aggregation of neighboring dissipates some of the captured energy before it can be used—a process known as aggregation-induced quenching.

Enomoto's team discovered a compound known as an aminobenzopyrano-xanthene (ABPX) dye that is not affected by aggregation. "We fortuitously discovered the ABPX dye in the process of synthesizing rhodamine B, another organic fluorescence dye," says Kamino. Investigating the compound's structure and photophysical properties in solution revealed that aggregate formation did not impede its energy-emitting performance (Fig. 1).

The researchers found that the key to the ABPX dye's improved performance despite aggregation is its extra bulk. The compound's carbon skeleton is almost twice as large as that of rhodamine B and incorporates side groups that prevent neighboring molecules in aqueous solution from stacking together too closely, something that causes molecules to rapidly dissipate their captured energy in other dyes.

An additional unique property of the dye is that it is readily converted into a singly charged 'monocation' or doubly charged 'dication' in response to its environment. Each ion emits light at a different wavelength, which the researchers believe can be exploited to make optical sensors. "We have developed for detecting target metal ions by taking advantage of this property," says Kamino.

The team are already working on new iterations of the dye that retain the useful aggregation properties while demonstrating improved light capture properties. "We are currently working on energy-conversion materials for organic ," Kamino says.

Explore further: The fluorescent future of solar cells

More information: Kamino, S. et al. A red-emissive aminobenzopyrano-xanthene dye: elucidation of fluorescence emission mechanisms in solution and in the aggregate state. Physical Chemistry Chemical Physics 15, 2131–2140 (2013).

add to favorites email to friend print save as pdf

Related Stories

The fluorescent future of solar cells

May 09, 2013

( —For some solar cells, the future may be fluorescent. Scientists at Yale have improved the ability of a promising type of solar cell to absorb light and convert it into electrical power by adding ...

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 ...

Recommended for you

A greener source of polyester—cork trees

Apr 16, 2014

On the scale of earth-friendly materials, you'd be hard pressed to find two that are farther apart than polyester (not at all) and cork (very). In an unexpected twist, however, scientists are figuring out ...

A beautiful, peculiar molecule

Apr 16, 2014

"Carbon is peculiar," said Nobel laureate Sir Harold Kroto. "More peculiar than you think." He was speaking to a standing-room-only audience that filled the Raytheon Amphitheater on Monday afternoon for the ...

Metals go from strength to strength

Apr 15, 2014

To the human hand, metal feels hard, but at the nanoscale it is surprisingly malleable. Push a lump of metal with brute force through a right-angle mould or die, and while it might look much the same to the ...

User comments : 0

More news stories

Hackathon team's GoogolPlex gives Siri extra powers

( —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...