White OLED is possibly the future generation of lighting source. A typical incandescent light bulb is roughly 12 lm/watt. (Lumen or lm is the unit describing the perceived power of light. Therefore, lumens/watt tells us how bright the light is generated per one watt.) The energy efficiency of conventional incandescent light bulbs is only about 4%. That is, for every 100 units of energy input to a light bulb, 96 units of energy are lost mostly in a form of heat. On the other hand, a fluorescent light, even with a much better efficiency up to 92 lm/W, poses an environmental problem due to the fact that it contains mercury which is hard to dispose and is harmful to an environment. The light produced is not an incandescent light; thus making it uncomfortable to human’s eyes. In addition, two types of these light bulbs are constrained by certain shapes. For example, fluorescent light always have to be shaped as a long tube. OLED lighting provides solutions to these problems.
OLED lighting uses the same technology as most OLED displays except that it only produces white light. Currently, the efficiency of white OLED is 102 lm/watt with a potential to reach up to more than 150 lm/watt according to Universal Display cooperation. Not only that, this OLED lighting is a thin sheet and does not have to be conformed into any specific shape. Imagine a wallpaper of paper-like light bulb. Because OLED composes mostly organic materials, it does not cause any environmental problem. The main setbacks with white OLED are that it can be easily damaged by water and the manufacturing cost is still too high to become a mass production. In year 2000, The U.S. Department of Energy established the solid-state lighting program which helps funding researches related to new generation of lighting. Universal Display, Philip, GE, and many other companies including government agencies are trying to push this OLED lighting technology forward, making the future of “greener light bulb” several steps closer to our home.
This is the fifth post of the Macroelectronics.org OLEDs series. Stay tuned.
Flexible OLED or FOLED is a very promising technology in the future. For FOLED to be flexible, metallic foils or thin plastics such as PET and PEN polyester films are used as the main substrate since it can endure strains very well. Because the display is flexible, it is less likely for the display to crack or break. Therefore, electronic products will last longer. Roll-to-roll process (found in printing industries) is an applicable manufacturing process, which will lower overall product costs. However, there are still many challenges before FOLED technology can be mass produced to the public. For instance, packaging FOLED is different than typical OLED. In order for typical OLED to be water resistance, two plates of thin glasses are sandwiched between the OLED. However, glass is brittle and it can not be used for FOLED where flexibility of the display is the key.
FOLEDs offer a new generation of display technology because they are durable, light weight, thin, flexible and cost effective. These qualities are ideal for mobile gadgets like cell phone, GPS, or even “smart clothing” where electronics are embedded within. Currently, companies such as Sony, Universal Display, Samsung, and US Army, are researching to make FOLED a feasible technology for everyday uses.
This is the forth post of the Macroelectronics.org OLEDs series. Stay tuned.
AMOLED, or active matrix OLED, is composed of an anode, a cathode, an organic layer, and a thin film transistor (TFT) matrix. Each pixel of the OLED is integrated onto a TFT array. TFT array controls the amount of current flows on each pixel which determines the brightness of generated light.
Instead of having external circuit to turn on/off the cathode and anode stripes that activate pixels in passive matrix configuration, AMOLED allows the current to flow through all of the OLED pixels while having TFTs controls how much current will each pixel gets. This is one of the advantages of AMOLED over PMOLED because TFT arrays need less power than external circuit. In addition, AMOLED’s pixel turns on and off at an incredibly rapid rate making it ideals for motion pictures. Though, AMOLED’s main disadvantage is its expensive manufacturing cost due to the intricacy of the active matrix structure that requires complex processes to fabricate.
Many leading display companies today such as Samsung, LG, Sony, Universal Display, Nokia and Kodak see a potential of and working on developing AMOLED displays. AMOLED now has become a promising technology for large display and portable display products.
The Passive-Matrix OLED or PMOLED is the first OLED to be commercialized. PMOLED is composed of anode strips, cathode strips, an organic active layer, and a substrate. Passive matrix is the configuration in which anode and cathode strips are arranged perpendicularly having an organic active layer in between. The intersections between anode and cathode strips are pixels. Light is generated when current passes through the selected anode and cathode strips. Therefore, turning on/off the current that goes through strips determined which pixels will be displayed and an image is created. Even though PMOLED is easy to fabricate and manufacture, the external circuit that controls current source is relatively expensive. Comparing to other OLED types, PMOLED is less efficient mostly due power loss from diodes and the strips. Though, this type of OLED still consumes less power than LCD display. Therefore, PMOLED is the most power efficient in and best used for small displays ranging from 2” to 3”. Currently they are used in cell phones, music players, GPS, and portable displays.
Flexible displays use up to 90 percent less materials by volume than conventional displays. The unbreakable displays were created by the FDC and HP using self-aligned imprint lithography (SAIL), a proprietary technology of HP Labs. SAIL is considered “self aligned” because the patterning information is imprinted on the substrate in such a way that perfect alignment is maintained regardless of process-induced distortion. SAIL enables the roll-to-roll printing manufacturing of the flexible displays.
It is expected that the flexible display market is to grow from $80 million in 2007 to $2.8 billion by 2013.
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More detail information can be found here on their "7 Areas of Innovation." Convenience and efficiency may be a great advantage to Nanosolar's thin-film technology, what also adds to the benefits of their product is the durability: the solar cells are able to withstand temperatures from -40 to +85 degrees Celcius, allowing them to be used virtually anywhere sunshine is plentiful.
Check out the following KQED video on Nanosolar:
(via Wikipedia & Nanosolar; Photo and video Courtesy: Nanosolar, KQED)
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