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17 Jun 2002
New organic compounds developed by European scientists could revolutionize light-emitting-diodes.
Researchers from Sweden's Linkoping University, and the University of Leece and Consiglio Nazionale Ricerche, Italy, have pioneered a breakthrough in the light-emitting-diode (LED) world. By tweaking the properties of oligothiophene compounds, organic materials that are typically used in field effect transistors, scientists have fabricated molecules with tunable multicolor electroluminescence emissions at previously unreported photoluminescence efficiencies.
"Thiophene compounds have always had poor photoluminescence efficiencies, so they haven't been fully exploited in LEDs," explained Giuseppe Gigli from Linkoping University. "However, we have found a class of oligothiophene that overcomes this problem."
The scientists noticed that substituting oxygen atoms into the thiophene compound, to produce an S,S-dioxide oligothiophene, increased photoluminescence efficiencies to 70%. They then altered the oligomer's chain length and rearranged its molecules to "tune" the electroluminescence emissions over the green to near-infrared regions.
Intent on commercialization, Gigli believes that the team first has to prolong the lifetime of the compounds. "For commercial applications, devices need at least 10000 hours of life," he said. "We have sold the patents to the Italian venture Salento Innovation Technology to do just this."
Another key application for the oligomers is biodiagnostics. "The materials are excellent candidates as markers for flow cytometry," added Gigli. "This is the subject of a spin-off with an Italian [biotechnology] company Bio-D."
The team now plans to look at second-generation optoelectronic devices, where photonic confinement can improve device performance.
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