When Samsung first released the GS5, we thought the 5.1" FHD Super AMOLED display is pretty similar to the 4.99" FHD one used in the GS4. But DisplayMate found out that this is a much superior display in many aspects, one of them being that it is 27% more efficient.
Samsung told DisplayMate that the improvement mostly came from more efficient OLED materials. They also incorporated new display electronics and optics and that helped as well. But now Chipworks posted a teardown of the GS5, and they published a macro image of the display's sub pixels. It turns out that it's a different architecture than the GS4, and this may explains some of the performance boost, too.
The GS4's display was the first OLED panel to use Samsung's new Diamond Pixel Pentile subpixel architecture. The display uses diamond red and blue subpixels and an oval green subpixel. In the GS5 display, however, all of the sub pixels are diamond shaped. The GS5 red and blue subpixels have a diagonal of about 27 µm while the green is smaller at 19 µm. The red and blue subpixels are smaller than the subpixels on the GS4 (in which the blue is 36 µm, the red is 31 µm and the green is 23 µ).