Multilayer slot-die coating of large-area organic light-emitting diodes

摘要

We investigate the slot-die coating process for the fabrication of large-area OLED lighting panels. Of many OLED layers, aqueous polymer-based hole injection layer (ML) and small molecule-based hole transport layer (HTL) are formed using large-area slot-die coating. We are faced with three technical issues related with slot-die coating such as the flow down of an aqueous polymer solution near the inner perimeter of an insulator bank, pinhole-like surface in solution-processed small-molecule films, and the dissolution between two stacked layers with different solvents. We have suppressed those phenomena to a great extent and demonstrated that OLEDs with slot-die coated multiple layers show almost the same device performance as a reference OLED device with spin-coated HIL and vacuum-evaporated HTL. The peak-to-peak roughness of the slot-die coated bilayer (HIL/HTL) films is observed to be less than 12.5 nm. The OLED device with the slot-die coated bilayer film exhibits the power efficiency of 27.2 lm/W at 1000 cd/m~2, which is even higher than that (25.5 lm/W) of the reference device.