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passive matrix OLED (PMOLED)

Unlike Active Matrix OLEDs (AMOLED), Passive Matrix OLEDs (PMOLED) do not have thin-film transistors for activation. The individual electrodes of PMOLEDs - the anode, the organic layer and the cathode - are arranged in rows in

the form of strips, with the rows of the anodes at right angles to those of the cathodes. The control can be done via the cathode and anode lines, whereby the Organic Light Emitting Diode (OLED), which is located at the intersection of the anode and cathode lines, is activated and emits light. The brightness depends on the injected current

.

Structure of the Passive Matrix OLED (PMOLED)

Structure of the Passive Matrix OLED (PMOLED)

Another control can be done by pulse width modulation (PWM). In this case, all cathode lines are simultaneously connected to ground and the organic pixels are driven via the anode lines with pulse width variation. This control is called single lineaddressing (SLA). The brightness of the OLEDs is controlled column-wise from the anodes using pulse width modulation (PWM). This means that certain OLEDs are switched on for shorter or longer periods of time and emit light. Thus, the overall brightness control is dependent on the row activation time and the pulse duration

at the anode.

Passive matrix OLED with pulse width control

Passive matrix OLED with pulse width control

OLEDdisplays made of PMOLEDs consume more power than those made of AMOLEDs, mainly due to the external control circuits. They are best suited for small screens and text displays, such as those used in PDAs and MP3 players.

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Englisch: passive matrix OLED - PMOLED
Updated at: 02.11.2010
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