Coverage Performance of PEDOT:PSS Against Particles on a Substrate for OLEDs

Abstract Short‐circuit defects caused by microscale dust particles in organic light‐emitting diodes (OLEDs) cause a decrease in production yield and hinder cost reduction. An organic layer coating by solution process is used to prevent short‐circuit defects of particles on a substrate. In this study, the coverage properties of a coated organic layer on size‐controlled particles are revealed. The surface of the substrate with size‐controlled SiO₂ particles with a diameter of 0.2–5 µm is quantitatively contaminated, and the particle coverage properties of the solution‐processed hole injection layer are investigated. From the results of the leakage current measurement and cross‐sectional observation by a transmission electron microscope, it is observed that devices with 50 nm‐spin‐coated poly (3,4‐ethylenedioxythiophene): poly(styrene sulfonate) can cover SiO₂ particles up to 1 µm in diameter without any increase in leakage current. It is revealed that larger‐sized particles cause electric defects, albeit with a low probability, owing to the larger space under the particles. To fabricate OLEDs with a high yield, the shape of the coverage at the bottom of the particle is important in preventing electric defects. The results of this study are useful not only for OLEDs but also for printed and coated devices.