Large area, full-color, digital image sensors made with semiconducting polymers

The high performance polymer photovoltaic cells and photodiodes demonstrated recently are of great interests not only for traditional applications but also for large area, digital image sensing. In this presentation, we demonstrate large sensing area, photodiode arrays and matrices made with semiconducting polymers and polymer blends. These photosensors are of high photosensitivity, low dark current, large dynamic range and fast response time. For full-color image sensing applications, large area photosensor arrays were developed to have true-color (24-bits) resolution. The red, green, and blue color primaries were achieved by coupling a set of color filters with the polymer sensor pixels with response to visible light radiation. Image recovery process from the pixel photocurrent data was developed, which is suitable generally to image arrays with power law light intensity dependence and with finite pixel dark current. Large sensing length photodiode arrays (2.5-5 in.) were fabricated in 40-100 dot-per-inch (dpi). They were used as the sensing unit in page-size document scanners. Voltage-switchable polymer photodetectors were developed. Their photosensitivity can be switched on and off with external bias. These devices can be used as the sensing elements in x-y addressable sensor matrices. The high on/off switching ratio and high photocurrent/darkcurrent ratio allow such two-dimensional, passive photosensor matrices to be used for image sensing applications. (C) 2000 Elsevier Science S.A. All rights reserved.