High performance, flexible polymer light-emitting diodes (PLEDs) with gravure contact printed hole injection and light emitting layers

The ultimate approach to organic semiconductor device fabrication is expected to be via high-speed, large area, roll-to-roll (R2R) printing. Gravure contact printing is one of the highest volume potential techniques, operating at speeds of over 35 m/min. Here we report high performance, flexible polymer light-emitting diodes (PLEDs) with gravure contact printed hole injection and emissive layers. We are able to successfully print highly uniform layers of optimum thickness of poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) and the light emitting polymer (LEP) LUMATION™ Green 1300. All the optimised formulations dry rapidly and evenly without solute aggregation and are compatible with fast processing on plastic substrates. PLEDs with the gravure printed layers have an identical performance to conventional spin-coated devices on the same substrate, achieving, at a display brightness of 100 cd/m2, luminosity, efficiency and drive bias values of 5.4 lm/W, 5.2 cd/A and 3 V, respectively. The devices achieve a maximum luminosity of 8.8 lm/W and a maximum luminance of 66,000 cd/m2, comparable to the performance range found for conventionally fabricated state-of-the-art green-emitting flexible PLEDs.