Inkjet-printing line film with varied droplet-spacing

Compared to the conventional cell-shaped pixel structure, linear bank structure for solution-processed organic light-emitting diode (OLED) displays has the advantage of simple process, and large aperture-ratio. However, the prolonged drying time of the inkjet-printed ink in the linear bank forms a convex surface profile in the longitude direction. To achieve uniform film surface of the inkjet-printed poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT: PSS), a novel printing method by varying the droplet-spacing is introduced. It is found that a larger droplet density at the line ends than that at the line center can compensate the inward flow of the ink, enabling systematic control of the film thickness along the line direction. As a result, uniform PEDOT: PSS line pattern is achieved. OLED display panels with line pixels are fabricated with varied droplet-spacing demonstrating better brightness uniformity than those inkjet-printed with constant droplet-spacing. (C) 2017 Elsevier B.V. All rights reserved.