Organic light emitting diodes (OLEDs) with thin-film passivation are expected to provide a means of producing next-generation flat-panel wide-area displays that are thin, lightweight, and flexible. Thick silicon nitride (SiN_x) films fabricated by a plasma-CVD method are already recognized as being a practical passivation film for OLEDs, but these are not suitable for automotive applications as cracks are generated in the films as a result of the thermal stress that is caused by the high temperatures that can arise in automobiles. To overcome this problem, we have developed plasma-CVD SiN_x / plasma-polymerized hydrogenated carbon nitride (CN_x :H) multi-layer films that increase the longevity of passivated OLEDs in automotive applications. The films exhibit a high barrier performance against moisture even at high temperatures, because the thermal stress in the films is released by the soft CN_x :H layers and no cracks are produced. Indeed, OLEDs with a multi-layer passivation film lasted over 1000 hours in driving tests at 85℃ (initial luminance = 400 cd/m²), while OLEDs with the thick SiN_x passivation film soon failed and no longer emitted light.

Takeshi Morikawa, Ryoji Asahi,
Takeshi Ohwaki, Koyu Aoki,
Kenichi Suzuki, Yasunori Taga

A new photocatalyst, known as nitrogen-doped TiO₂ (TiO_2-xN_x), yielding high reactivity under visible light irradiation, together with high potential for mass-productivity, has been developed by using a highly time-efficient development technique that combines compu-tational materials design with experimental syntheses. Under visible light irradiation, TiO_2-xN_x films and powders exhibit significant advantages over commercially-available TiO₂ in terms of optical absorption and photocatalytic decomposition rates with respect to gaseous acetaldehyde and toluene, etc. The active wavelength range of TiO_2-xN_x (below 520 nm) covers a wider irradiation energy range for white fluorescent and incandescent light than that of TiO₂. As a result, TiO_2-xN_x exhibits a photodecomposition rate for gaseous acetaldehyde that is more than 5 times higher than that of TiO₂ under interior illumination (300-600 lux). It also exhibits significant antibacterial properties. TiO_2-xN_x is therefore a promising photocatalytic material, and it possesses other desirable features; it shows highly reproducible photocatalytic activity, it has a potential for mass-production, and it is environmentally benign (no toxic ingredients). Further development of this material is now underway, so it should be available to contribute to the human environment by reducing indoor VOCs (Volatile Organic Compounds) in the very near future.