Japan Display - a joint venture consisting of Sony, Toshiba and Hitachi -? revealed the development of a 5.2-inch OLED smartphone screen featuring 1,080p resolution and 423 pixels per inch.

The full HD OLED screen offers a RGBW pixel layout, which is a screen technology that offers an extra-white subpixel alongside the traditional red, green, and blue pixels; this addition enhances brightness and battery life in comparison to regular OLED displays and LCDs.
japan display oled.jpg

This OLED screen stacks up nicely in comparison with the two current smartphone heavyweights with LCDs: HTC's One packs a 4.7-inch screen with 468 ppi, and Sony's Xperia Z uses a 5-inch display with 443 ppi. Samsung's Galaxy S4 and its Super AMOLED screen contains a whopping 441 ppi, but that figure isn't directly comparable in this situation since the S4's display uses PenTile screen tech -- meaning the S4 utilizes subpixel rendering and contains one less subpixel.