Samsung's Galaxy S4 smartphone is causing excitement with its 4.99" AMOLED panel with Full HD resolution (1920?1080). But how did Samsung manage to improve the resolution of its AMOLED panel?
At the end of 2012, many Full HD smartphones used LTPS TFT LCDs. Due to challenges with the evaporation process higher resolutions are generally more difficult for AMOLED. As long as HD (1280 x 720) was the standard smartphone resolution, AMOLED has been able to compete. But with Full HD (1920 ? 1080) displays starting to become the new standard for high-end smartphones, AMOLED faces challenges.
Samsung has been using its proprietary Pentile sub-pixel layout to enhance resolution. But according to DisplaySearch expert David Hsieh, Samsung's Galaxy series has benefitted from steady improvements in AMOLED resolution by modifying the Pentile pixel structures.
Earlier this year, Samsung demonstrated a 4.99" Full HD AMOLED panel, but did not disclose any technical details. Hsieh believes that Samsung has revamped its sub-pixel layout to achieve FHD resolution using its existing FMM (Fine Metal Mask) evaporation process. He claims that Samsung might be using the advanced s-stripe with hexagonal and diamond-shaped pixels to achieve the higher ppi. According to a previous sub-pixel structure on which Samsung has filed a patent, it is possible that the diamond-shaped sub-pixel structure will be as shown below:
The s-stripe arrangement has several advantages. First, the display readability is significantly improved compared to traditional Pentile, which has two sub-pixels per pixel. S-stripe has three sub-pixels per pixel, and an advanced design may have five. The second advantage is that s-stripe may enable longer lifetimes for the display. Normally, the blue organic material has the shortest lifetime; in s-stripe, the blue sub-pixel domain is larger than that of the other colors. This means that the luminance per area can be less for blue, which is less stressful. In this way, the entire OLED display's lifetime can be extended.
"If an s-stripe or advanced version sub-pixel layout is the ultimate solution for AMOLED to achieve 400 ppi+ resolution, then it could be a competitive advantage for Samsung," Hsieh said.