The Passive-Matrix OLED or PMOLED is the first OLED to be commercialized. PMOLED is composed of anode strips, cathode strips, an organic active layer, and a substrate. Passive matrix is the configuration in which anode and cathode strips are arranged perpendicularly having an organic active layer in between. The intersections between anode and cathode strips are pixels. Light is generated when current passes through the selected anode and cathode strips. Therefore, turning on/off the current that goes through strips determined which pixels will be displayed and an image is created. Even though PMOLED is easy to fabricate and manufacture, the external circuit that controls current source is relatively expensive. Comparing to other OLED types, PMOLED is less efficient mostly due power loss from diodes and the strips. Though, this type of OLED still consumes less power than LCD display. Therefore, PMOLED is the most power efficient in and best used for small displays ranging from 2” to 3”. Currently they are used in cell phones, music players, GPS, and portable displays.
(via howstuffworks, universal display ; image credit: howstuffworks and danawa.com)