Self-aligned bilayer inkjet printing process for reducing shadow area by auxiliary electrodes in OLED lighting

Abstract

Auxiliary electrodes are a key component for uniform luminance of large area organic light emitting diode (OLED) lighting. A shadow area is created by the auxiliary electrodes covering the light emitting area of ​​the OLED, reducing the light emitting area. To minimize the shadow area of ​​ printed auxiliary electrodes, we developed a self-aligned bilayer inkjet printing (SABP) process. A silver-insulator bilayer was self-aligned by a hydrophobic bank where the ink did not spread. Through the SABP process, the insulator was covered with a width that was about 400 nm wider than the width of the Ag electrode. In addition, electro-optical characteristics such as luminance, current density, current efficiency, and external quantum efficiency of 40 × 40 mm 2 OLED lighting were measured to confirm the effect of the fabricated auxiliary electrodes. The luminance non-uniformity of the OLED lighting with the printed auxiliary electrode was 17%. For OLED lighting, inkjet-printed auxiliary electrodes provide potentials comparable to those of vacuum-deposited auxiliary electrodes. • Self-aligned bilayer printing patterns the silver-insulator of an auxiliary electrode for OLED lighting. • The auxiliary electrode is printed with a height of 1.09 μm and a width of 21.1 μm. • The insulator covers the width of the Ag electrode with a margin of 400 nm wide. • Self-aligned bilayer printing is effective in reducing a shadow area by auxiliary electrodes. • The luminance non-uniformity of OLED lighting with printed auxiliary electrodes is 17%.