Michele Ricks's Posts
OLED Technology & the Environment - Part II
One of the reasons I love working in OLED technology is because it has the potential to reduce the environmental impact of displays.
An important advantage of OLED technology is that no heavy metals are used in fabricating the displays. LCDs commonly rely on compact fluorescent lamps, containing mercury, as a light source. Mercury is toxic to humans and animals. Since OLEDs do not contain mercury, they can reduce the environmental impact of displays and lower disposal and recycling costs.
Green Tip of the Day: Don't throw away your old electronics with LCD displays - there's mercury in that panel!
One of the main attractions of OLED technology, compared with LCD, is that it is a simpler structure. Both OLEDs and LCDs use LTPS TFT substrates, but OLEDs require fewer materials to create a full-color display. Schematics of typical AMOLED and AMLCD displays are shown below. Fewer materials used in OLEDs results in less waste to be disposed of or recycled later!
An important advantage of OLED technology is that no heavy metals are used in fabricating the displays. LCDs commonly rely on compact fluorescent lamps, containing mercury, as a light source. Mercury is toxic to humans and animals. Since OLEDs do not contain mercury, they can reduce the environmental impact of displays and lower disposal and recycling costs.
Green Tip of the Day: Don't throw away your old electronics with LCD displays - there's mercury in that panel!
One of the main attractions of OLED technology, compared with LCD, is that it is a simpler structure. Both OLEDs and LCDs use LTPS TFT substrates, but OLEDs require fewer materials to create a full-color display. Schematics of typical AMOLED and AMLCD displays are shown below. Fewer materials used in OLEDs results in less waste to be disposed of or recycled later!
OLED Technology & the Environment
A really cool thing about OLED technology is that it's useful for lighting, as well as displays. The US Department of Energy (DOE) has an Energy Star Program for Solid State Lighting (SSL) aimed at reducing the amount of energy consumed by light bulbs and fixtures.
The key to lighting is that you want it to be white. As you may know, there are many different kinds of white. You can buy "warm white" or "cool white" light bulbs. "Warm whites" tend to appear slightly yellow, while "cool whites" have more of a blue component. The DOE has specified a range of color temperatures that are acceptable for its lighting project.
You may have also noticed that colors of objects appear differently under different types of light. For instance, navy blue and black may look like the same color inside under an incandescent lamp, but they will look like markedly different colors outside in daylight. This effect is described by the color rendering index (CRI), which explains how naturally colors are reproduced by a light source.
Engineers and scientists in my group are developing OLED architectures and materials suitable for white-lighting applications. Recently, Kodak demonstrated an OLED device architecture having an efficacy over 55 lm/W! This is 5X the efficiency of the common incandescent light bulb and similar to the best compact fluorescent lamps. Kodak's remarkable architecture exceeds the efficacy specification requirements of the Department of Energy (DOE) Energy Star Program for Solid State Lighting (SSL) while maintaining a color temperature and CRI that meet the specifications.
The performance improvements for OLED SSL at Kodak will contribute toward more environmentally friendly lighting in the future. So when will you have an OLED light in your home or office? Market research companies, such as Nanomarkets, predict early product applications of solid state lighting for architectural and specialty lighting in the next few years. They estimate OLED lamps for general illumination will be available in 2011.
The key to lighting is that you want it to be white. As you may know, there are many different kinds of white. You can buy "warm white" or "cool white" light bulbs. "Warm whites" tend to appear slightly yellow, while "cool whites" have more of a blue component. The DOE has specified a range of color temperatures that are acceptable for its lighting project.
You may have also noticed that colors of objects appear differently under different types of light. For instance, navy blue and black may look like the same color inside under an incandescent lamp, but they will look like markedly different colors outside in daylight. This effect is described by the color rendering index (CRI), which explains how naturally colors are reproduced by a light source.
Engineers and scientists in my group are developing OLED architectures and materials suitable for white-lighting applications. Recently, Kodak demonstrated an OLED device architecture having an efficacy over 55 lm/W! This is 5X the efficiency of the common incandescent light bulb and similar to the best compact fluorescent lamps. Kodak's remarkable architecture exceeds the efficacy specification requirements of the Department of Energy (DOE) Energy Star Program for Solid State Lighting (SSL) while maintaining a color temperature and CRI that meet the specifications.
The performance improvements for OLED SSL at Kodak will contribute toward more environmentally friendly lighting in the future. So when will you have an OLED light in your home or office? Market research companies, such as Nanomarkets, predict early product applications of solid state lighting for architectural and specialty lighting in the next few years. They estimate OLED lamps for general illumination will be available in 2011.
How OLED Technology Works
For those of you curious about how the OLED display works in Kodak's new AMOLED Wireless Picture Frame , here's a little tutorial.
Organic light emitting diode (OLED) technology uses substances that emit red, green, blue or white light when excited with an electric current. Without any other source of illumination, OLED displays present bright, clear video and images that are easy to see at almost any angle.
OLED displays stack up several thin layers of materials - a human hair is 200 times thicker than the total organic stack! As current passes through the device, the organic materials are excited. In techno-jargon, holes and electrons from the electrodes recombine to form an excited state of the emitting molecule. In order to relax again, the excited molecule gives off light that we see through the transparent substrate. Different colors of light are achieved by doping (mixing in an additive) the organic material with compounds designed to emit the desired wavelength of light.
The OLED display in Kodak's wireless picture frame is an Active matrix (AM) OLED display. These displays are fabricated on glass sheets using a low-temperature polysilicon (LTPS) semiconductor layer to build thin-film transistors (TFTs) at each point in the display (pixel) that switch the pixel on and off. The combination of TFTs and other integrated electronics (drivers) allow pixels to stay on longer and reduce the size of the display module. The use of LTPS TFT substrates also enables high-resolution (small pixels) displays that deliver smooth, high-quality video and can be scaled to sizes needed for TVs.
The OLED display is built in a multi-step process. First, the LTPS TFTs are built on a large glass substrate, the "motherglass." This is moved into a low-pressure environment for addition of the OLED layers. Next, another piece of glass is sealed to the substrate, encapsulating the OLED layers, to protect the device from oxygen and moisture. Finally, individual displays are cut from the motherglass. Many small displays can be made on motherglass sheets that can be as large as a queen-size bed!
Organic light emitting diode (OLED) technology uses substances that emit red, green, blue or white light when excited with an electric current. Without any other source of illumination, OLED displays present bright, clear video and images that are easy to see at almost any angle.
OLED displays stack up several thin layers of materials - a human hair is 200 times thicker than the total organic stack! As current passes through the device, the organic materials are excited. In techno-jargon, holes and electrons from the electrodes recombine to form an excited state of the emitting molecule. In order to relax again, the excited molecule gives off light that we see through the transparent substrate. Different colors of light are achieved by doping (mixing in an additive) the organic material with compounds designed to emit the desired wavelength of light.
The OLED display in Kodak's wireless picture frame is an Active matrix (AM) OLED display. These displays are fabricated on glass sheets using a low-temperature polysilicon (LTPS) semiconductor layer to build thin-film transistors (TFTs) at each point in the display (pixel) that switch the pixel on and off. The combination of TFTs and other integrated electronics (drivers) allow pixels to stay on longer and reduce the size of the display module. The use of LTPS TFT substrates also enables high-resolution (small pixels) displays that deliver smooth, high-quality video and can be scaled to sizes needed for TVs.
The OLED display is built in a multi-step process. First, the LTPS TFTs are built on a large glass substrate, the "motherglass." This is moved into a low-pressure environment for addition of the OLED layers. Next, another piece of glass is sealed to the substrate, encapsulating the OLED layers, to protect the device from oxygen and moisture. Finally, individual displays are cut from the motherglass. Many small displays can be made on motherglass sheets that can be as large as a queen-size bed!