Fully organic imager unveiled

The imager is sensitive in the wavelength range between 500 and 600nm, making it suitable for X-ray imaging applications. It was fabricated by thermally evaporating an ultra thin photosensitive layer of small organic molecules (SubPc/C60) on top of an organic readout circuit. A semi-transparent top contact enables front-side illumination. The readout backplane was manufactured on 6in foil laminated wafers. It consists of pentacene based thin film transistors in arrays of 32 x 32 pixels with varying pitch (1mm and 200µm). The imager was characterised under illumination with a calibrated green led, yielding a linearly increasing photocurrent from the incident power of 3µW/cm2. Dark current density is below 10 to 6A/cm2 at a bias voltage of -2V. Paul Heremans, technology director at the imec/Holst Centre, said: "This latest achievement is a significant step forward in not only finding the optimal materials, but pinpointing the best ways to process materials into reliable organic circuits and systems with state of the art performance."