Europium Complexes Emit Red Light with Record Efficiency

New material developed in Poland has enabled Scottish researchers to produce a highly efficient, nearly monochromatic red OLED.

The compounds were developed at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw using phosphine oxides as co-ligands in europium ion-based complexes. A research group from Scotland's University of St. Andrews, collaborating with the Polish Academy, used the compounds to build prototype OLEDs.

Red light emitted by the europium complexes with phosphine oxides is of well-defined wavelength, about 612 nm. The luminescence quantum yields of these compounds reach 90 percent, according to the researchers.

Record efficient luminescence of europium complexes with phosphine oxide co-ligands is demonstrated. Courtesy of Institute of Physical Chemistry of the Polish Academy of Sciences.

"We attach extended, highly rigid phosphine oxides to europium complexes,” said Michal Maciejczyk, a doctoral student at the Polish Academy. “As a result, the energy delivered to the molecule is not dissipated in unnecessary vibrations or rotations. Instead of delivering heat to the surroundings, we have higher efficiency and virtually monochromatic light.”

The new complexes do not degrade when exposed to oxygen or light. According to researchers, the materials could be collected in films from solutions, rather than the expensive vacuum evaporation and deposition process used to manufacture OLED films today.

Potential applications of the new materials include not only OLEDs, but also flexible elastic dermal patches for use in anticancer therapies. The europium complex-based compounds incorporated in such patches would generate light of a precise wavelength that could activate treatment drugs delivered with other methods to patients’ skin cells, having only minor effects on patient mobility and perhaps eliminating the need for hospitalization.

The research was funded by the Polish National Science Centre.

For more information, visit: www.ichf.edu.pl.