Small OLED screens are being used in millions of devices already (like in Samsung's Galaxy S phones or Sony's upcoming portable console Vita), but we're still waiting for large-sized models to hit the mainstream. It's been four years since Sony offered the XEL-1 (a mini OLED TV) in stores, but the industry has been innovating on LCD screens, for example with LED backlight or 3D, since.One of the biggest problems is cost: producing big OLED screens has simply been too expensive so far. But now Japan-based Sumitomo Chemical has reportedly developed a technology that makes it possible to mass-produce large OLED TVs at reasonable prices.source