Sony developed a new OLED Panel with Self-aligned Top-gate Oxide TFT. With this technology the image quality was improved by reducing the uneveness of brightness.
Sony showcase a 9.9 inch OLED prototype and a pixel count of 960 x 540 at the SID-2011. The brightness of this panel is 200cd/m2 with an all-white signal and 600cd/m2 or higher at its peak. The contrast ratio is 1.000.000:1 or highter with a color gamut of 96% on NTSC standards.
With a self-aligned top-gate structure, the channel length of TFT becomes short, making it easy to deal with large screen size and high resolution of OLED panels as well as increase in drive frequency.
The problem of the brightness unevennes of OLED panels is that there is a problem of parasitic capacitance that is generated between the gate electrode and source/drain electrode of TFT (thin-film transistor). The value of the parasitic capacitance fluctuates on some parts of the screen, generating brightness unevenness.
Sony developed a new manufacturing process technology. It consists mainly of four processes: (1) patterning with a dry-etching method after forming oxide semiconductor IGZO (indium gallium zinc oxide), gate insulating film and gate electrodes on a glass substrate, (2) forming an aluminum (Al) thin film on it with a sputtering method, (3) forming an aluminum oxide (Al2O3) protective layer by oxidizing Al in an oxygen annealing process and a low-resistance layer by dispersing enzyme on the surface of the oxide semiconductor and (4) forming source/drain electrodes by opening via holes after forming an organic layer in a coating process.
Source:TechON
