Comparison of passive matrix (PMOLED) and active matrix (AMOLED)

The PMOLED is simply formed into a matrix by a cathode and an anode, and illuminates the pixels in the array in a scanning manner. Each pixel operates in a short pulse mode and is an instant high-luminance illumination. The advantage is that the structure is simple, and the manufacturing cost can be effectively reduced. However, the driving voltage is high, making the PMOLED unsuitable for application on large-size and high-resolution panels, which is different from the current development.

Therefore, the OLED screen that we are currently in contact with, whether it is a smartphone or an OLED TV, is also an AMOLED screen. Therefore, when I see the term AMOLED, it is not necessary to think that it is more advanced than OLED. The two are actually a kind of thing. Although we all call Samsung and LG's 55-inch TVs as OLEDs, in fact, these two TVs are also AMOLEDs. There is no such thing as OLEDs used in TVs and AMOLEDs are used in small and medium-sized screens.

Passive Matrix OLED (PMOLED)

The PMOLED has a cathode strip, an organic layer, and an anode strip. The anode strip and the cathode strip are perpendicular to each other. The intersection of the cathode and the anode forms a pixel, that is, a portion where light is emitted. The external circuit applies a current to the selected cathode strip and anode strip to determine which pixels are illuminated and which are not. In addition, the brightness of each pixel is proportional to the magnitude of the applied current.

PMOLEDs are easy to manufacture, but they consume more power than other types of OLEDs, mainly because they require external circuitry. PMOLED is the most efficient for displaying text and icons, and is suitable for making small screens (2-3 inches diagonally), such as those that people often see on mobile phones, palmtops, and MP3 players. Even with an external circuit, the passive matrix OLED consumes less power than the LCDs currently used in these devices.

Active Matrix OLED (AMOLED)

The AMOLED has a complete cathode layer, an organic molecular layer, and an anode layer, but the anode layer is covered with a thin film transistor (TFT) array to form a matrix. The TFT array itself is a circuit that determines which pixels emit light and determines the composition of the image.

AMOLED uses a separate thin-film transistor to control each pixel. Each pixel can drive light continuously and independently. It can be driven by low-temperature polysilicon or oxide TFT. The advantage is low driving voltage and long life of light-emitting components. However, the high cost and manufacturing process are more complicated and more difficult to control in terms of cost.

AMOLEDs consume less power than PMOLEDs because TFT arrays require less power than external circuits, making AMOLEDs suitable for large displays. AMOLED also has a higher refresh rate and is suitable for displaying video. The best use of AMOLEDs is in computer displays, large screen TVs, and electronic signage or billboards.