Mitsubishi is a "community" that consists of a multitude of independent companies involved in a wide range of markets including automobiles, plastics, electronics, hotels, banking and more. Several of these companies are involved with OLEDs:
Mitsubishi Chemicals is working towards OLED materials together with UDC. They have also entered the OLED Lighting market together with Pioneer in February 2010 and are selling OLED panels under the Verbatim brand (Verbatim is owned by Mitsubishi Chemicals).
Mitsubishi Heavy Industries has decided to start making OLED display panels back in 2007, although we did not hear about these efforts since.
Mitsubishi Electric are producing the world's largest OLED display, the Diamond Vision OLED. These are modular displays that are made from 128x128 PMOLED tiles. Those displays are already available and the first one was installed in 2010 at Merck's Material Research Center.
1-1 Marunouchi 1-chome