The base of PQi's screens are LCD screens, just a bit more optimized.
(thinner screen,some plastic layers removed), but the very essence is still an LCD screen.
They optimized the polarization filters to not have that 'green-grey-ish' look normal LCD's have.
They reduced the thickness of the LCD by a small margin,
they used a reflective background, be it reflector type or just a plain white plastic I don't know.
Probably use LED backlight too.
If they did not, I assure you you could make a screen like this yourself at home, and have about the same effect (provided if you know how to remove and paste some polarization filters on the LCD, which can be tricky because pasting always leaves bubbles like a sticker does unless you have some device to paste them without bubbles).
Also, I have not yet seen the right polarization filter. they sell some filters on
http://www.polarization.com/ but I have not yet seen completely transparent ones.
Most of them are light grey at best.
If you would be able to do that, you would end up with a screen probably not as efficient as PQi's in contrast, but you will have the same battery benefit.
On some laptops you can use the original pol filters, you just need some reflective background.