Three-color passive-matrix pixels using dye-diffusion-patterned tri-layer polymer-based LED

Dry dye-printing and solvent-enhanced dye diffusion were used to locally dope a previously spin-coated poly(9-vinylcarbazole) (PVK) polymer film with different dyes to fabricate side-by-side RGB OLED pixels. To reduce reverse leakage current and raise efficiency, a blanket tris-8-hydroxyquinoline aluminum (Alq) electron transport layer (ETL) was deposited over the polymer layer after the dye diffusion step, along with a 2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline (BCP) hole/exciton blocking layer between the Alq and the PVK to ensure all light emission occurred from the doped polymer and not from the Alq. Devices with this tri-layer structure have an extremely low reverse leakage current (rectification ratio of 10⁶ at +/- 10V) and a higher external quantum efficiency (∼1%) than single layer devices. A three-color passive-matrix test array with 300μm × 1mm RGB subpixels was demonstrated with this structure.