Multilayer OLEDs with four slot die-coated layers
For the first time, multilayer OLEDs with four solution-processed layers have been fabricated step-by-step using slot die coating.
A suitable choice of coating parameters and fluid formulation enabled the application of different material classes as large-area homogeneous layers with thicknesses in the nanometer range. The AFM measurements of the slot die-coated layers consisting of small molecules showed Ra values of 0.21–0.28 nm, less than previously reported in the literature.
70% higher efficiency
Based on a two-layer reference OLED consisting of a HIL and EML, the stack architecture was first extended by a crosslinked HTL. These three-layer OLEDs with a crosslinked HTL achieve 70% higher efficiency, compared to that of the reference devices, thus assuming successfully separated layers.
In a further step, an additional ETL has been applied via the orthogonal solvent approach to obtain four solution-processed layers. The averaged power efficiency of the four-layer OLEDs is increased by a factor of 2.2 compared to the reference OLEDs up to a value of 3.5 lm/W.
Based on these results, it can be assumed that both approaches, the use of orthogonal solvents as well as the application of crosslinkable materials, have been successfully combined to fabricate multilayer OLEDs with four separated slot die-coated layers.
The study can be found in Journal of Coatings Technology and Research, Volume 16, Issue 6.
Image source: Pixabay.
