• Fledderus, Henri
• Yakimets, Iryna
• Mandamparambil, Rajesh
• Schaubroeck, David
• Hoegen, Thomas
• Naithani, Sanjeev
• Van Steenberge, Geert

Abstract

The fast growing market of organic electronics, including organic light emitting diodes (OLEDs), stimulates the development of versatile technologies for structuring thin-film materials. Ultrafast diode-pumped solid-state (DPSS) lasers have proven their full potential for patterning transparent conductors, but only few studies report on interaction with thin-film barrier layers. Indeed, in the case of flexible organic applications, thin-film barrier layers consisting of inorganic and sometimes inorganic/organic multi-layers are usually used for protection. This severely restricts the selection of suitable laser patterning conditions, as damaging the barrier stack will result in moisture and oxygen ingress, leading to accelerated device degradation. In this paper we present picosecond laser processes for selective patterning conductive polymers like poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), without damaging the barrier, as well as for selective patterning the top encapsulation, without damaging the anode or cathode contacts. Careful examination using optical profilometry, SEM and chemical surface analysis reveals the importance of the laser wavelength (1064nm, 532nm, 355nm), pulse duration, pulse frequency, pulse energy, spot size, laser fluence, and pulse overlap. The fundamental laser material interaction is discussed for thin-film material stacks, and the material removal is believed to be driven by photomechanical and photochemical processes. After optimisation of the individual processes, the development of generic subtractive laser processes for industrial OLED manufacturing is discussed, with focus on process quality and speed.

Topics

• impedance spectroscopy
• surface
• polymer
• scanning electron microscopy
• Oxygen
• profilometry