Many bloggers have picked up on comments that Philip Berne of Samsung made at a recent press event. He explained that the reason that Samsung chose PenTile Super AMOLED over RGB stripe AMOLED was that of lifetime, specifically that of blue subpixels. He is exactly right, but let me explain this a little more.
AMOLEDs have lifetime that is related to the current density used to drive the OLED material. This is especially true for blue since blue has the lowest brightness for a given amount of current. The other way to say this is that blue OLED material has lower luminous efficiency. To maintain the same brightness with blue, OLED display designers have to drive it with more current per unit area.
So how does PenTile technology help Samsung to extend lifetime for high resolution panels?
This comes from the ability to use 2/3s the number of subpixels in PenTile OLED (Super AMOLED) relative to RGB stripe OLED (Super AMOLED Plus). Thanks to PenTile technology’s use of subpixels rendering it is possible to have the same number of pixels as the equivalent RGB stripe. With only 2/3s the subpixels, one can make the ratio of driven subpixel area larger with a smaller overall percentage of space in between subpixels (better fill factor), as compared to RGB stripe – which is what gives rise to the improvement in current density for a given brightness, which in turn leads to better lifetime.
For lower pixel pitch, such as was used in the Galaxy S Plus, the current density was relatively low due to the coarser pixel pitch so the lifetime was fine. But, at the pixel density of the Galaxy Nexus or the Galaxy S III, PenTile is the way to go, at least until sometime in the future when significant strides are made in blue OLED material luminous efficiency. As I have said before, PenTile is an enabler that make high resolution OLED practical for the product brightness and lifetimes specs that we all have come to demand. This is why you have never seen any production OLED of greater than 250 dpi without a PenTile configuration. If the demand for ever increasing pixel pitch continues, PenTile will still be key even if blue luminous efficiency sees some level of enhancement.