Electroluminescence of Coumarin-Based Dyes

A comparative study of electro- and photoluminescence properties of a novel coumarin dye and coumarin 6 is presented. It is shown that the electroluminescence spectrum of the new dye is red-shifted by 12 nm compared with its photoluminescence spectrum in a toluene solution. This result is explained by the presence of an anthracene-based group in the new coumarin dye, which prevents the formation of a dimeric structure in the organic light-emitting diode (OLED) active layer. Therefore, exciton emission prevails in electroluminescence in contrast to coumarin 6 emission caused by dimers. With the same OLED structures and almost identical I—V curves, significant differences in the voltage–luminance characteristics are observed, which are explained by the difference in electron mobilities of the studied compounds.