Ink Jet Technology for Large Area Organic Light-Emitting Diode and Organic Photovoltaic Applications

Abstract

Due to its flexibility and ease of patterning, ink jet printing has become a popular technique for the noncontact deposition of liquids, solutions, and melts on a variety of substrates at lateral resolutions down to 10 lm. This article presents a study of ink jet printing of homogeneous layers of Orgacon TM (Agfa-Gevaert, Belgium), a water-based dispersion of poly(3,4-ethylenedioxythiophene):poly (styrenesulfonic acid) (PEDOT:PSS). The printed PEDOT:PSS layer can be used as a transparent electrode in organic light-emitting diodes (OLEDs). Fundamental aspects of the interaction between the ink jet ink and the substrate and the resulting homogeneity of the active layer in relation to OLED device performance are investigated. The optimized PEDOT:PSS ink formulation is shown to improve layer homogeneity, resulting in a uniform light output and device efficiency. Ink jet printing is shown to be capable of fabricating 25 Â 25 mm OLED devices that have equivalent efficiency and light uniformity to the ones produced by spin coating.

How PEDOT:PSS solutions produce satellite-free inkjets

“…Figures 1b and 2 imply that elastic responses of the PEDOT:PSS solutions can not significantly contribute to the satellite production. As surfactants take time (typically > 10 -2 s for dynamic surface tension lowering [4]) to reach fresh surfaces, ink-jet satellite production should be enhanced for all of the aqueous solutions. However the major difference here between shear thinning ( Figure 1a) and Newtonian fluids in terms of satellite formation could be due to a difference in their viscosity at the low shear rates relevant to fluid motion in the ligament.…”

“…Aqueous dispersions of PEDOT:PSS with or without surfactants have been successfully deposited by inkjet printing for some years to form transparent conductors in printed electronics [1][2][3][4][5][6][7][8], but it has only recently become apparent that their main and satellite drop formation across a wide range of speeds is unusual in comparison with most other printable polymeric fluids.…”

Inkjet Printing of Functional Materials for Optical and Photonic Applications

“…Inks of this polyelectrolyte system have been prepared and processed by using inkjet for the manufacturing of OLEDs [116,126,127,128]. Control of the PEDOT:PSS ratio, the solvents employed or the addition of surfactants to inks, strongly influence the morphology and the electric properties of the final applied materials after solvent evaporation [129].…”

Direct Motion Planning for Vision-Based Control

“…If a display is a rigid structure (i.e., the pitch between OLED cells is equal) and the location of the display is known at all times, the printing task could be executed with a constant velocity and a constant drop-on-demand (DOD) print-frequency [17]. Existing research adopting this technique can be found in, e.g., [18] and [19], an overview of inkjet-based micro-manufacturing is given in [20]. However, due to the flexible nature of the display and the absence of a proper fixation system, a designed trajectory is a necessity.…”

“…For the printing task, the print-head shoots a polymer droplet, which has a diameter of 50 [ ], at the center of each OLED cell (see Fig. 3 and [19]). In order to execute an accurate printing task, the delay of the printing task itself needs to be taken into account.…”