OLED Lighting: Coming of Age
by Mike Hack
OLEDs are now catching the attention of the consumer. OLED smart phones can be found in every store and are offered by all the major carriers. Fabulous early-entry OLED TVs are now available on a limited basis and offer truly spectacular visual experiences. While the early focus of OLED development was for flat-panel-display applications, through the use of phosphorescent OLEDs, energy-efficient solid-state lighting is now also being realized.
Lighting is at a cross roads. Incandescent lamps are being banned worldwide because of their environmental impact, while compact fluorescent lamps have limited visual appeal, as well as safety concerns with regard to residential lighting due to their mercury content. Both LEDs and OLEDs provide safe and efficient replacements for these older lighting technologies and can complement each other in how they are used. LEDs offer bright point-source illumination, while OLEDs are large-area, thin, diffuse sources of light. Of course, pricing will have a major impact on how widely each approach is adopted by the marketplace.
Many companies have now expressed their interest in developing OLED lighting products, from panels to luminaires. Over the next few years, we will see a range of these products enter the marketplace, and it will be very exciting to see how consumer reaction shapes and drives this industry.
In this special issue, we have three diverse perspectives on the promise and reality of OLED lighting. Starting with a key technology developer, Universal Display Corp. (UDC), we see how its phosphorescent-OLED technology is a critical element for OLED lighting to become an energy-efficient, visually pleasing, thin, and high-quality source of area illumination. Samsung SMD develops this theme, expanding on how the inherent characteristics of OLED lighting inspire a revolutionary change in solid-state-lighting applications. From Samsung's perspective as a leader in OLED-display manufacturing, the authors describe the key issues for the production of OLED lighting panels. In our third article, Acuity Brands Lighting explores the value proposition for OLED lighting for the consumer from its position as a global luminaire company with an extensive portfolio and market share in all lighting technologies.
UDC discusses how phosphorescence is a key enabling technology that may enable OLEDs to become a new appealing and energy-saving form of solid-state lighting. UDC describes its recent results, including a 15 cm x 15 cm panel that exceeds 50 lm/W. OLEDs are shown to have very desirable color quality, and the UDC authors outline their recent progress in improving their all-phosphorescent white device lifetimes. OLEDs offer a radically new view of lighting – until now, all lighting has been based on point or linear sources of light, and OLEDs break this mold by providing inherent area lighting. Examples of prototypes showing transparent PHOLED light art and flexible light sources add to the excitement of the possibilities offered by this new technology.
Samsung SMD also suggests that the inherent characteristics of OLEDs, such as ultra-slim thickness, transparency, flexibility, and color changeability can provide an opportunity for OLEDs to be a new revolutionary lighting source. The authors describe some of the technologies under development for OLED lighting to meet efficiency and lifetime requirements, including phosphorescence for its efficiency, tandem device architectures for extended lifetime, PIN doping for further reductions in device voltage, and the importance of cost-effective light extraction. They point out that today, given that phosphorescent OLEDs enable nearly 100% internal quantum efficiency, effective outcoupling is perhaps the largest efficiency loss and therefore the largest area for efficacy improvement. They believe that OLED lighting has a considerably wide market window, from premium-grade decorative lighting to general lighting, and several key factors such as frequency of use, operational cost over time, visual comfort, and specific design parameters need to be considered. Finding a collective solution among these parameters to reduce the cost will be ultimately crucial for the commercial success of OLED lighting. Finally, the authors consider the challenges for the mass production of OLED lighting panels.
Acuity Brands Lighting introduces its article from the company's perspective as a major supplier to the approximately US$50 billion annual global lighting-fixture market. The authors see great potential for OLED lighting because the diffuse nature of OLED lamps is ideal for both commercial and residential markets – which together represent a 60% share of the lighting market. They outline their current roadmap for OLED panel efficacy and lifetime as OLED lighting products mature. Acuity Brands Lighting is currently leading the charge in demonstrating OLED fixtures, and the authors show photographs of two revolutionary OLED luminaires that Acuity exhibited at LightFair earlier this year.
Given the momentum that is now developing, OLED lighting seems to be at the tipping point. If the technical performance and cost targets can be realized in the next few years, OLED lighting will have a significant impact on reducing our energy consumption and provide an elegant and appealing solution to many of our lighting needs. The revolutionary form factors enabled by thin, flexible, and transparent OLEDs will really transform the way we use and see light. •