Simplified, yellow, organic light emitting diode by co-evaporation of premixed dye molecules

We fabricate light-emitting layers consisting of a matrix material as well as a green and orange-red dye. These co-doped emitting layers are realized by two different methods. The first is the classical co-evaporation with different evaporation sources for the three different molecules. The second evaporates a premixed blend of the two dyes from one source and the matrix from another, reducing the number of needed evaporation units. Except for this variation, the layers are identical and the process is used to realize individual layers as well as complete OLEDs. Both fabrication techniques produce devices with similar efficiencies and mixed, yellow-orange spectra. Nevertheless, the second one has the advantages of less complicated machine layouts and a much easier deposition rate control which potentially reduce the process complexity for large scale industrial production. Yet, the changing composition of the mixture in the common crucible still remains a problem.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights►Two different techniques for co-doped organic layers are compared. ► Results for individual layers and complete OLEDs are very similar. ► The evaporation including a premix of dyes in a crucible allows for a balanced emission. ► Reproducibility of this technique remains an issue.