Study of the interference effects in an optical cavity for organic light-emitting diode applications

The interference effects generated in a bottom-emitting electroluminescent device fabricated on a polymer underlayer introduced with the aim of improving the anode roughness have been studied. The analysis of the interference fringes at different detection angles and the spatial coherence demonstrates that this phenomenon is due to multiple internal reflections that propagate in the polymer layer. This effect can be eliminated by modifying the polymer thickness and the incidence angle of the electromagnetic radiation at the anode-polymer interface. Inkjet etching technology is adopted for microcavities-shaped polymer structuring to destroy the resonator effect of the optical cavity.     

A Study on Thermal Degradation of Organic LEDs Using IR Imaging

In this paper, we present a correlation study between the working temperature of OLEDs (Organic Light Emitting Diodes) and the electroluminescence and driving voltage changes. The aim is to investigate the relationship between the operating temperature and the aging mechanisms. We have found that performances degradation of devices is strictly related to the glass transition temperature (T_g) of organic layers, and that electrical failure is reached only for temperatures higher than T_g.     

Influence of substrate temperature on the chemical and microstructural properties of MO-CVD ZrTiO<Subscript>4</Subscript> thin films

In the last few years, intensive research activity has been focused on the development of suitable synthesis methods for high-permittivity materials, used for the realization of next-generation microdevices able to fulfil the previsions of the Technology Roadmap of Semiconductors. The use of high-permittivity materials can overcome the difficulties concerning the production of SiO₂-based ultra-thin dielectrics, such as the generation of pinholes and the non-uniformity of the film, which may result in a malfunction in high-density systems. Recently, zirconium titanate thin films were discovered to have very interesting dielectric properties, which suggests a use for them in microwave integrated systems, such as receivers or DRAMs, since they are monophasic, have little dissipation and show a good thermal stability and a high value for the dielectric constant, independent of frequency in the range from kilohertz to a few gigahertz. Real application is possible only in strict connection with the development of a suitable preparation method which allows production with controlled and reproducible characteristics. In this work, the synthesis and characterization of Zr_xTi_1-xO₄ (ZT) thin films grown via MO-CVD is described, studying the influence of growth parameters on their structural, chemical and physical properties. Received: 17 June 2002 / Accepted: 24 June 2002 / Published online: 4 November 2002 RID="*" ID="*"Corresponding author. Fax: +39-06/9067-2445, E-mail: Pad@mlib.cnr.it     

PANI-CSA: An Easy Method to Avoid ITO Photolithography in PLED Manufacturing

In order to optimize polymer light emitting diode (PLED) performances, devices with holes injected through an Indium Tin Oxide (ITO) / Polyaniline (PANI) electrode into the polymer are much more efficient than devices fabricated with the anode made only by ITO. We demonstrated that by using doped PANI as hole injection layer in a polymer light emitting diode the manufacturing process can become simpler. Indeed, the pattern of conductive layer can be produced without ITO photolithography by UV exposition. As hole transporter layer, Poly(N-vinylcarbazole) (PVK) was spin coated over the doped PANI layer and a layer of tris (8-hydroxy) quinoline aluminum (Alq₃) was then thermally evaporated so as to form the electron transport layer. To complete the device structure, Aluminum contacts were deposited onto the organic layers by vacuum evaporation at low pressure. The layers were characterized by X-ray small-angle diffraction, IR Raman and UV-Vis spectroscopies. Devices without PANI and with PANI as HIL were studied.