All quality eReaders of today use eInk technology as it is the only screen surface that gives you a non backlight, high resolution and long battery life 
experience. This is required in order to give an acceptable e-reading experience. I love this technology but am coming to the realisation that there are other screen technologies that could not only do the same thing but do it so much better.
OLED is one of those technologies and I don’t think it will be too long before we start to see these as the new trend in eBooks, most probably being released through mobile devices. It deals with the prerequisites of reading on electronic devices and starts to provide a few more, here is why;
- No backlight – OLED does not need a backlight to function, this means that there is not a light competing with the sun etc… with OLED the ability to read in all the same environments as a traditional book becomes possible.
- High resolution – OLED resolution matches and could exceed that of eInk
- Battery Life – because there is no need for a backlight the battery life is greatly extended as it only needs to power the pixels being used. In the case of eBooks the amount of pixels that need to be active is much lower than other applications such as video.
- Portable – the screen is as thin as .3 millimeter.
There are also some added advantages
- It is full color and capable of showing video
- It can bend, making it possible to make things fold out. This gives the potential for incorporating into mobile devices that can fold out to give a bigger reading experience as required
- The production process could be cheaper than LCD screens
Read more on LED with these links
http://en.wikipedia.org/wiki/Oled
http://electronics.howstuffworks.com/oled1.htm
This is it! I was looking for article like this one couse I need it for my home work.