Large‐Area Inkjet‐Printed OLEDs Patterns and Tiles Using Small Molecule Phosphorescent Dopant

Abstract

AbstractThe main bottleneck in inkjet printing (IJP) is a stable and jettable ink formulation. This paper discusses the ink formulation for the small molecule phosphorescent dopant/host system. The study involves the estimation of Hansen solubility parameters (HSP) to formulate inkjet‐printed ink of an iridium complex‐based phosphorescent material, bis(4‐phenylthieno[3,2‐c]pyridinato‐N,C2') (acetylacetonate) iridium(III) (PO‐01) as dopant and 4, 40‐bis (carbazol‐9‐yl) biphenyl as the host of the emissive layer. Based on dopant and host HSP analyses, toluene and methyl benzoate are chosen as ink solvents. Our ink is stable for a month and can be replicated with great accuracy. The interaction of individual drops is examined in detail since resolution or film quality is highly influenced by the drop formation and spread on a substrate. Finally, an inkjet‐printed emissive layer is demonstrated on both glass and flexible substrates. The fabricated devices exhibit the maximum current efficiency and luminance of 6.4 cd A−1and 5781 cd m−2. A technique is also shown to print large‐area organic light‐emitting diode (OLED) devices having different patterns without patterning or pixelization of the active area of the electrodes. Up to 80 × 80 mm2large‐area OLED tiles are made using IJP of the emissive layer.