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OLED is a type of LED where the light comes from organic materials/organometallic materials rather than inorganic materials in traditional LEDs.
 
Moreover, OLED has pixels that are basically individually backlit, meaning your blacks are true black, and will not have a haze from turning the brightness up too high like LCDs do. No matter the brightness, black is black, because the black pixels are technically turned off until needed.
 
Lcd & led

Simple Facts:

LED= Light Emitting Diode
LCD= Liquid Crystal Display

All iPods, since the iPod Photo at least, have been LCD Displays with LED Backlight.
http://support.apple.com/kb/SP66

The iPhone & Touch are different as the display is also the touch sensor. Apple's Tech Specs leave out any mention of the display lighting technology, but that may be due to them wanting to keep tight lipped about the sensor tech in the display.

CFLs are by no means big. Only in the last couple years have cellphones switched to LED lighting & the screens aren't big. You're thinking of CRTs (or Cathode Ray Tubes) which are bigger & not flat, thus the TUBE.

Depending on size, power regulation & brightness levels, LEDs use 10-60% the power of CFLs
 
This is kind of a funny topic, as I don't believe you could ever make cold cathode fluorescent lights small enough to fit inside a cell phone.
 
Cell phones have used LED backlights since the very beginning. I really doubt the existence of CCFL backlit displays on phones.
 
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