3, Trovato Manufacturing, Inc, Victor, New York, United States
2, Microcontinuum, Inc, Cambridge, Massachusetts, United States
Extracting the “internally waveguided” light from OLEDs, which together with losses to surface plasmons at the metal cathode typically account for > 50% of the light generated in the emission zone, has proven to be a particularly challenging problem. To address this problem, we describe devices fabricated on nano-patterned plastic substrates that disrupt the internal waveguiding and surface plasmon modes. We describe thermally evaporated small molecule phosphorescent OLEDs (PhOLEDs) fabricated on corrugated polycarbonate (PC) and polyethylene terephthalate substrates nanopatterned in a roll-to-roll process. We compare the devices fabricated on glass/ITO to those on plastic/PEDOT:PSS. Depending on the height and pitch of the pattern, up to a 2.5 fold increase in the outcoupling factor is observed relative to the flat substrate, resulting in green and blue PhOLEDs with an external quantum efficiency that reaches 50% and 32%, respectively. Issues related to the fidelity of the conformal deposition of the various layers on the patterned plastic, imaged by AFM and focused ion beam (FIB), are also discussed.