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We present a thin-film dual-layer bottom barrier on polyimide that is compatible with 350°C backplane processing for organic light-emitting diode displays and that can facilitate foldable active-matrix organic light-emitting diode devices with a bending radius of

Side leakage experiments have been performed on the organic interlayer, so-called organic coating for planarization (OCP), in a hybrid thin-film encapsulation (TFE) stack based on two silicon nitride (SiN) barrier layers that was developed for organic light-emitting diodes (OLED). To measure the side leakage into OCP, a metallic Ca thin-film monitor can be used. However, the water uptake capacity of the Ca monitor affects the measurements. Here, we eliminated the contribution of the Ca layer from the measurement by variation of the Ca thickness and by measuring the side leakage until it reaches the Ca layer. For OCP with a water getter inside (5% CaO) the side leakage can be monitored by the loss of scattering of the CaO when it reacts with water to Ca(OH)2. This work describes measurements of the rate of side leakage into the OCP layer of the TFE stack, both for plain OCP and for OCP with CaO getter inside. The side leakage curves are used to derive diffusion coefficients. Performing measurements at various climates provides acceleration factors that are relevant for the performance quantification of the TFE stack. The limiting factors on the performance of an unstructured TFE stack as produced in a roll-to-roll (R2R) process are presented. For small OLED devices side leakage would drastically reduce the shelf lifetime but for larger devices the permeation properties of the TFE stack determine the shelf lifetime.

A technique is presented on tracing the sub-micron pinholes that result in black spots in organic light-emitting diodes (OLED) when exposed to ambient atmosphere. The mystery about the type and nature of tiny pinholes present in the OLED cathode that allow oxygen and/or moisture ingress in minute quantities causing black spot formation, is clarified. The technique can accurately locate nanodefects or pinholes in the center of black spots of various sizes, even on a centimeter scale. Pinholes in the investigated OLEDs were shown to be caused by different particles originating from various locations in the device stack. Defects in the Ba-Al cathode of a solution processed polymer LED (PLED) and pinholes in the LiF-Al cathode of a thermally evaporated small molecule organic LED (smOLED) were investigated and compared. The technique is a powerful tool for inspection and can, thereby, accelerate the process optimization for OLED fabrication.

The requirement for evaluating high performance barrier layers with water vapor transmission rates (WVTR) far below 10−3 g/m2 d has been sparked by the growing application of flexible and organic electronics. While several highly sensitive WVTR-measurement techniques are described in the literature, their accuracy and comparability has not yet been tested. There is an absence of direct comparison of these methods. With a growing body of literature referring to different coating and barrier technologies (often under different testing conditions), it is extremely difficult to gather a coherent picture both of the performance of the materials studied and the permeation measurement methods used. In order to clarify these points we report on independent WVTR measurements of the same batch of a high performance barrier film under two sets of conditions in several laboratories with different state-of the-art methods. These methods also include several calcium test set-ups. The results showed that, while some differences are present, there is a remarkable level of agreement between the measurement methods even prior to harmonization.

The availability of a high performance thin-film barrier is the most critical challenge in upscaling and commercializing flexible OLED products. We report a flexible thin-film-barrier technology that meets lifetime specifications for OLED lighting, and demonstrate it in rollable QVGA a-IGZO AMOLED displays. Roll-to-roll manufacturing of this high performance barrier film will be presented. cop. 2013 Society for Information Display.

To protect organic flexible devices from the ambient, they have to be encapsulated. Depending on the application in mind (OLED lighting, PV) different thin-film encapsulation methodology can be chosen. Each encapsulation process has different requirements and fabrication process freedom might be restricted, for example by mechanical reliability requirements or the total cost of the end product. Here we will show our recent investigations into different thin-film barriers with respect to their application and the route to production.

A new method of making ultra-thin flexible organic light emitting diodes (OLEDs) using standard OLED fabrication facilities is reported. Through use of the Electronics on Plastic by Laser Release (EPLaR) technology, we have developed and demonstrated 18-μm thick single-pixel OLEDs. In this paper, besides describing the fabrication method, the electrical and optical performance of the flexible OLEDs is reported.

Organic light-emitting devices (OLEDs) have attracted considerable interest in the last five years and are now viewed as an important competitor with liquid crystals for a wide variety of display applications. Current research focuses on the use of small-molecule and polymer materials to make organic electroluminescent displays with both passive-and active-matrix technologies. This article will discuss work on the device architecture for a polymer passive-matrix display application, the stability of polymer light-emitting displays, and the use of ink-jet printing for high-resolution patterning of red, green, and blue light-emitting polymers.

Polymer LEDs have a number of attractive properties that make them suitable for many applications. Operating at low voltage, bright large-area devices can be made by simple technology. One of the limitations that prohibited industrialization of polymer LEDs was their limited lifetime. An overview of the improvement of polymer LED performance at Philips is presented. The progress during the last year is reflected by lifetimes of many thousands of hours for 8 cm2 devices that operate at daylight visibility under ambient conditions. Diagnostic measurements have been performed on polymer LEDs before and after stress testing, and on the materials used in these devices. These measurements have contributed to the understanding of the nature of the degradation of polymer LEDs.

Highly transparent OLEDs are very attractive for lighting and light beautification applications. While the transparent anode is based on transparent ITO, the transparent cathode is based on a 3-layer approach: (semi)transparent electron injection layer that is a low work function metal, electrically transparent conductor used in order to limit the voltage drop across the OLED area, and overcoat to tune the optical properties without influencing the electrical properties. Transparent encapsulation based on thin film technology is used in order to protect devices from ambient exposure. Using this approach large area (50 cm2) transparent organic light-emitting device having 75% transparency in the off state is demonstrated. The efficiency of the transparent OLED is comparable with that of bottom emission OLED. It is demonstrated that by tuning the thickness and optical properties of both the cathode and the encapsulation the amount of light emitted through the anode and the cathode can be varied while the total amount of light emitted by the OLED remains the same. Moreover device optimization based on optical thin film calculations has been performed such that no angular dependence of emitted light is present both on anode and cathode side.

We present results and a discussion of highly efficient polymer Light-Emitting Diodes (polymer LEDs, PLEDs). The external quantum efficiency in current standard devices reaches up to 2-4% only. We have explored two routes to enhance this value. In the first route, PEDOT/PSS is replaced with a novel anode or hole injection layer. The efficiency with some Light Emitting Polymers (LEP) is improved significantly, resulting in an efficacy of 35 cd/A for a yellow emitting poly-(para-phenylene-vinylene) and 20 cd/A for a blue emitting poly-(spirobifluorene). We attribute the major improvement compared to standard devices, where about 10 and 5 cd/A are obtained, respectively, to a combination of improved exciton formation efficiency and light out-coupling efficiency, and to less quenching of the radiative decay under actual device operating conditions. In the second route, we developed a new host polymer with high triplet energy such that transition metal-based green-emitting phosphorescent dyes can be used without significant back transfer of triplet excitons to the polymer host. First results using this system showed about 25 cd/A using a soluble green Ir-based emitter. Importantly, all data are obtained in a standard two-layer device of a hole transport/injection layer and the LEP.

The status of the development of full-color polymer light emitting diodes will be presented. The focus of current materials research is on state-of-the-art red, green, and blue light-emitting polymers (LEP) with high efficiency, optimum color points, low driving voltages and long lifetimes in devices. A general overview of the progress of red, green and blue LEP lifetimes and efficiencies will be given and compared to requirements for both full-color passive and active matrix-displays for mobile display applications. Further, the status of ink-jet printing of LEPs for the industrialization of full-color displays will be discussed, and a comparison of the performance of spin coated and inkjet printed devices will be presented. In addition, two material-related topics studied recently will be discussed; namely, the lifetime of blue light-emitting devices correlated to processing, anodes, cathodes and the blue polymers themselves, and second, the consequences of pulsed-driving schemes on efficiency and lifetime.

In this paper on polymer LEDs we discuss the formation of black spots, surface treatments of the anode, and photochemical degradation of the emissive polymer. We find that small pinholes in the cathode layer are the origin of the black spots. The black spots form when H2O or O2 diffuse through the pinholes and react with the cathode at the polymer-cathode interface.A model is presented that describes the growth of the spots. We find that for both indium-tin-oxide (ITO) and Au anodes, an UV/O3 or an O2 plasma cleaning treatment increases the work function by 0.8-0.9 eV. A higher work function may lead to a better hole injection and a reduction in the operating voltage. We present a method to measure the quantum yield for bleaching, (gamma) equals 1.6$MN4 and (gamma) equals 1.7 10-7 for bleaching of dialkoxy-PPV in air and vacuum, respectively, indicating that the polymer is 1000 times more stable in vacuum than in air.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Royal Philips Electronics has recently launched the first commercially available polymer Light Emitting Diode (LED). In this paper, physical properties and phenomena will be discussed that must be taken into account during the selection of a polymer material and the choice of the device structure; for example, color, electron and hole mobility, polymer thickness, lifetime, leakage current and failure.