Roll-to-Roll Fabrication of PEDOT:PSS Stripes Using Slot-Die Head With <inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>-Tips for AMOLEDs

Abstract

Stripe coating offers an approach to remove the pixel bank structure used to confine ink droplets. For potential application in solution-processable active-matrix organic light-emitting diode displays, we fabricate fine and dense stripes of poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate)(PEDOT:PSS) using a slot-die head with the dual plate (shim plate with slit channels and meniscus-guiding plate with μ-tips as narrow as pixels). We analyze the flow distribution of the aqueous PEDOT:PSS solution near the μ-tip by varying the dual-plate configuration (μ-tip width, μ-tip length, and shim plate thickness) together with the process variable (i.e., coating speed) and offer design guidelines for the roll-to-roll fabrication of a fine stripe pattern. It can be achieved by reducing the μ-tip length as well as the shim plate thickness and increasing the coating speed until the flow breaks up. This scheme also enables us to raise the stripe density without defects. It is found that the μ-tip length is crucial for coatings of dense stripes. If μ-tip is long, it is not feasible to fabricate dense stripes regardless of the shim plate thickness due to an increase in resistance to flow. It is also found that the wettability of the solution serves as one of the critical parameters that determine the stripe profiles. We have fabricated 100 stripes with the average width of 227 μm and interstripe width nonuniformity as low as 9.2%. Finally, we have fabricated organic light-emitting diodes (OLEDs) atop the conductive PEDOT:PSS stripes and successfully obtained light emission from OLED stripes.