OLED Showcase exhibited on international Convention of Lighting Designers

Transparent OLEDs have been focal point in extraordinary application study

OLEDs (Organic Light Emitting Diodes) are close to prime time and OSRAM Opto Semiconductors is among the leading companies in the development of OLED Lighting products. International architectural lighting design companies are paying close attention to the rapid progress in this field. The ability of an large area light source to be transparent when turned off and to evenly emit light in the on state is a unique feature of OLED technology. Transparency is regarded as second wave in OLED Lighting. During the Professional Lighting Design Convention in Berlin the unlimited facets of OLED Lighting was discussed with the community of lighting professionals.

Light effects by OLED lighting

Source: OSRAM

OLED Lighting Application Scenarios

Key for OSRAM Opto Semiconductors is the development of OLED light sources for general space illumination, and large-area light-emitting elements. What characteristics of this new light source offer designers new possibilities?

One has to go back to the foundations of architectural lighting design to understand the true potential of this new technology. Richard Kelly, the first architectural lighting designer who worked with Mies van der Rohe on the Seagram Building in Chicago, defined the essence of light in space: ambient luminescence, focal glow, and play of brilliants. Ambient luminescence provides general illumination of the surrounding space. Focal glow accentuates important objects and informs the occupant. It emphazises objects that we need or want to see. "Play of brilliants" is "light to look at" - chandeliers, sparkle, beautiful luminaires or projected light patterns that are the highlight of the space.

Where does OLED fit in? Actually, in all of the three lighting phenomena. First, OLED luminaires will provide "ambient luminescence" for general illumination. In the very near future, a hybrid approach of LED and OLED sources can already be combined in pendant luminaires for office lighting where, say, 300 Lux is needed. Pure OLED luminaires - pendant or task - will be possible in two or three years. Can the second lighting phenomenon - focal glow - be achieved at all? Actually, yes. Since illuminance is intensity over distance squared, the key is distance. In other words, retail lighting and energy efficient lighting of the future will use undercabinet and furniture integrated OLEDs close to the illuminated objects. But why not use other lamps? Metal halide, fluorescent and low voltage incandescent lamps become too hot and contain too much UV (and often also too much light) for expensive items on display. This leads to surface deterioration (such as cracks) and color fading. In this regard, LEDs and OLEDs are optimal sources. What is the potential of OLEDs over LEDs, then? OLEDs have three advantages. First, they are very thin and very elegant. The OLED in the off-state is already an appealing mirror that no other lamp can match. Second, its spectrum is broad. This creates a natural object appearance, whereas LEDs tend to be very vivid, a character that not suit some artwork. Third, OLEDs create soft shadows and soft large highlights. This combination creates very interesting lighting effects. They lead to a very expensive, elegant look of jewellery, shoes, transparent and translucent material, and other glossy and semiglossy objects.

But can we create a "play of brilliants"? If we define it as sparkle, the answer is no. However, "play of brilliance" is also defined as "light to look at". It is fascinating to look at candles, the moon, or reflections of sunlight in a creek. The same is true for OLED chandeliers! They create a calm play of pure, soothing light that is impossible to create with other sources.

The Tutanchamun Showcase

We highlighted the potential of OLEDs by lighting a life-size replica of Tutanchamun. All surfaces of the pharao are gilded or painted and come close to the original appearance. We were interested in creating soft highlights and shadows and to demonstrate the potential of OLED for museum lighting, where lighting requirements are most stringent. OLEDs were integrated in a square vitrine made up of acrylic glass panels and mirrors at the top and bottom. What surprised us most was the  refined and faithful color rendering even of "monochromatic" OLED panels. A simple combination of amber and blue yields already a fairly full spectrum. Even amber OLEDs can be used to light human skin. We combined white, blue and red bottom emitters (opaque panels) with several transparent white OLED. By varying the voltage, we changed the on-state appearance from diffuse to clear. The effect was visualized by having a female model looking through the transparent OLED into the vitrine. This creates a stunning effect - the OLED becomes a material that reflects like a mirror, emits light like a diffuse fluorescent lamp and is transparent like glass.  All effects are combined in one slim pane that is 150 mm square and 1 mm thick. This is a new lighting material with unmatched potential for existing and new applications in lighting design.