Effects of plasma polymerized para-xylene intermediate layers on characteristics of flexible organic light emitting diodes fabricated on polyethylene terephthalate substrates

Characteristics of flexible organic light emitting diodes (FOLEDs) with the plasma polymerized para-xylene (PP pX) intermediate layer were investigated. For the purpose of reducing moisture permeation through plastic substrates, a PP pX intermediate layer was inserted between FOLEDs and the plastic substrates. As the concentration of C–H bonding in the PP pX film deposited at 25 °C was increased, PP pX films showed increased transmittance. Surface morphologies of polyethylene terephthalate (PET) covered with the PP pX intermediate layer were improved compared to PET without PP pX on it. Due to the highly cross-linked network structure in the plasma polymer film, water vapor permeability of PET substrates with the PP pX intermediate layer of 75 nm was decreased compared to PET substrates without PP pX on it. FOLEDs with the PP pX intermediate layer showed improved optical and electrical characteristics as well as lifetimes than FOLEDs without the PP pX intermediate layer.