Archive for February, 2009

Flexible OLED

February 28, 2009

LEDs (Light Emitting Diodes) make use of  the direct recombination of minority carriers (holes or electrons) to emit photons.
The emissive layer is usually P-type (more holes) substrate because the diffusion length for electrons are longer (meaning larger emmisssion volume) – electrons would be injected into the P-type substrate from the N-type (more electrons) substrate.  
OLEDs (Organic Light Emitting Diodes) make  use of a film of organic compounds as the emissive electroluminescent layer. This time, the emissive layer is N-type, because in organic semiconductors holes are more mobile than electrons.
Because the organic substrate used can be flexible, we got a flexible LED display.

Advantages

– Because each pixel emits light on it’s own, there is no need for a backlight as in the case of LCDs. Hence there is power -savings.

-OLEDs enable a greater range of colors, gamut, brightness, contrast (both DR and static) and viewing angle than LCDs because OLED pixels directly emit light. OLED pixel colors appear correct and unshifted, even as the viewing angle approaches 90 degrees from normal. LCDs cannot show true black because they use a backlight, while an “off” OLED element produces no light and consumes no power.
  
Disadvantages

-The biggest technical problem for OLEDs is the limited lifetime of the organic materials. In particular, blue OLEDs historically have had a lifetime of around 14,000 hours (5 years at 8 hours a day) when used for flat-panel displays, which is lower than typical lifetime of LCD, LED or technology—each currently rated for about 60,000 hours, depending on manufacturer and model. Toshiba and Panasonic have come up with a way to solve this problem with a new technology that can double the lifespan of OLED displays, pushing its expected life past that of LCD displays. A metal membrane helps deliver light from polymers in the substrate throughout the glass surface more efficiently than current OLEDs. The result is the same picture quality with half the brightness and a doubling of the screen’s expected life. 

Ideas for applications: Perhaps these flexible displays could replace textbooks, since they can withstand bending stress, and their low power consumption makes portability feasible. This means less strain on young schoolgoers.

Sources:
http://en.wikipedia.org/wiki/OLED

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Clean Room MV

February 7, 2009

I never expected anyone would make a music video in a clean room!