Highly sensitive permeation measurements are crucial for the characterization and development of polymeric substrates for flexible display applications. In particular, organic light-emitting devices require substrates with extremely low permeation rates for water and oxygen. Here we demonstrate a concept for measuring ultralow permeation rates. The amount of oxidative degradation in a thin Ca sensor is monitored by in situ resistance measurements. The benefits of this technique are demonstrated for polyester foils with single- and double-sided barrier coatings. A sensitivity limit is imposed by the quality of the encapsulation. The resulting base line contribution to the water vapor transmission rate of a glass reference is below 10−6 g/m2 day at accelerated test conditions.

Due to their outstanding properties, e.g., good contrast, wide viewing angle, low power consumption, and self-emission organic light-emitting (OLE) displays on the basis of conjugated polymers are on the verge of commercialization. Two major disadvantages of the current processing technique for the polymers—spin coating—are the material waste and the difficulties involved in patterning multichrome or even full-color displays. Therefore, we investigated the screen-printing technique for the production of OLE displays. In this letter, we present performance data and images of screen-printed OLE diodes. They are already comparable to spin-coated ones. We observed luminance of 10 000 cd/m2 at 8 V and peak efficiencies exceeding 10 cd/A for green diodes. These data indicate that printed organic displays have the potential to replace “classical” spin-coated devices.

Organic light-emitting diodes were fabricated on a 125-μm-thick polyethylene terephthalate substrate covered with 100 nm indium tin oxide. The luminance–current–voltage performance and the emission spectrum of the devices are investigated in the bent state under mechanical stress at different bending radii. Down to a curvature of 15 mm, no significant decrease in the device performance is found compared to the relaxed state, as well as to conventional devices on glass substrates.

Abstract. We focus on the determination of the internal luminescence quantum efficiency of a green-emitting organic light-emitting diode (OLED). By considering different geometrical configurations of OLED thin-film stacks, we elucidate the role of the internal luminescence quantum efficiency of the emitter in the thin-film microcavity. Combining optical simulations with experimental results, a comprehensive efficiency analysis is performed. Here the electroluminescence of a set of OLEDs is characterized. Additionally, the devices are characterized using time-resolved photoluminescence measurements. The experimental data are analyzed using optical simulations. This analysis leads to a quantification of internal luminescence quantum efficiency and allows conclusions about competing mechanisms resulting in nonradiative recombination of charge carriers. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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