Polymer light-emitting diodes with thermal inkjet printed poly(3,4-ethylenedioxythiophene):polystyrenesulfonate as transparent anode

Conjugated poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) films, prepared by inkjet-printing and spin-coating methods, have been studied using atomic force microscopy, micro-Raman spectroscopy, photoelectron spectroscopy, and four-point probe conductivity measurements. Electrical conductivity of the inkjet-printed film was enhanced by a factor of around 10 when compared to a spin-coating film. The improved conductivity was attributed to longer effective conjugation length of PEDOT chains in inkjet-printing PEDOT:PSS films as suggested by their micro-Raman spectroscopy. PEDOT:PSS films formed by the inkjet-printing method are appropriate for use as an anode for simplification of the fabrication process of polymer light-emitting diodes whose performance is about 1.2 cd/A.