Drivers, OLEDs

The upper limit for passive matrix OLEDs thus depends on many factors, including the reverse current of the diodes, the current delivery of the row drivers, the roll-off in OLED power efficiency, and the brightness and contrast ratio requirements of the application. The practical limit is probably less than VGA resolution (480 rows by 640 x 3 columns, where the factor of 3 reflects the RGB subpixels for color) for power-sensitive portable applications. However, such considerations are less important where a wall-plug is available and one company in Japan (Idemitsu Kosan [190]) has demonstrated full color television using passive OLED arrays. 

Can access many types of databases given an appropriate ODBC driver or OLE database. 

Power Consumption of AMOLEDs for Three Sets of OLED Emitters (Portion on Pixel Driver Is Excluded)... 

In the article by the Pflaum and Sokolowski groups (Chapter 8, by Voigt et al.) a related dielectric, AI2O3 deposited on a transparent conductor, indium tin oxide, ITO, is used to fabricate pentacene-based OFETs. Such devices are particularly interesting in connection with the manufacture of drivers for OLED displays. 

The passive matrix consists of a set of row electrodes and column electrodes, with an OLED formed at each intersection. A row is selected for light emission by applying a select voltage pulse, forward biasing the diodes in that row. Currents proportional to the image data for the selected row are applied to the column lines by the driver circuits. All the unselected rows are reverse biased. 

The advantage of AMOLED over PMOLED displays arises because emission in a passive matrix occurs one line at a time, so each OLED element operates at high peak currents and low duty-cycle. The duty-cycle in a PMOLED display is approximately equal to the inverse of the number of rows. For example, in an SXGA (1280 X 1024) display, the duty cycle is approximately 0.1%. The peak current of an OLED pixel may be 1 mA or more. High OLED currents lead to reduced power efficiency and operational lifetime and also place greater demands on the current capacity of the row driver circuits, which may have to handle currents of hundreds of miUiamperes on each output (although not simultaneously). 

Fig. 7.1. Two architectures for display driving, (a) shows a single transistor architecture appropriate for latching and holding charge on the pixel for field driven display elements such as liquid crystal displays or e-Ink. (b) schematically shows the matrixed version of this element, (c) shows a two transistor voltage-programmed current driver appropriate for OLEDs. More advanced voltage and current programmed circuits are also possible, but require more transistors.

As in the case of OLEDs, the primary driver for considering polymeric materials for OTFTs is the possibility of rendering them soluble by addition of appropriate side chain functional groups. The orientation of the molecules in the resulting films... 

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