TOLED – Transparent OLED

http://electronics.howstuffworks.com/oled4.htm

TOLEDs use a “proprietary transparent contact to create displays that can be made to be top-only emitting, bottom-only emitting, or both top and bottom emitting (transparent)…70% transparent when turned off – TOLEDs may be integrated into car windshields, windows, eyewear and may be used with other opaque substrates for top-emitting devices.
http://www.oled-info.com/glossary