ACTIVE MATRIX – BACK PLANE

In an active-matrix display, each pixel is connected to its corresponding row and column electrodes by one or more transistor switches. These transistors allow the pixel to remain in the defined ‘on’ or ‘off’ state, even when the row in which the pixel resides is not being addressed. The image represented by each row of pixels therefore remains static until the row is re-addressed, eliminating the possibility of flicker.





Further development of large, flexible displays requires a cost-effective manufacturing process for the active-matrix backplane, which contains one transistor per pixel. One way to further reduce costs is to integrate (part of) the display drive circuitry, such as row shift registers, directly on the display substrate. Here, we demonstrate flexible active-matrix monochrome electrophoretic displays based on solution-processed organic transistors on 25-m-thick polyimide substrates. The displays can be bent to a radius of 1 cm without significant loss in performance. Using the same process flow we prepared row shift registers. With 1,888 transistors, these are the largest organic integrated circuits reported to date. More importantly, the operating frequency of 5 kHz is sufficiently high to allow integration with the display operating at video speed. This work therefore represents a major step towards 'system-on-plastic'.