Optical Image and Color Recognition Using Monolithic Tandem Pinip and Pinpin Heterojunctions: A Comparison

Optimized a-SiC:H multilayer devices based on two different tandem configurations (TCO/pinpi´n/TCO and TCO/pini´p/TCO) are compared and tested for proper image recognition and color separation process using an optical readout technique. In both configurations the doped layers are based on a-SiC:H to increase image resolution and to prevent image blurring. To profit from the light filtering properties of the active absorbers, the intrinsic layer of the front diode (i layer) is based on a-SiC:H and the back one (i´ layer) on a-Si:H. The effect of the applied voltage on the color selectivity is discussed. Results show that the relative spectral response curves demonstrate rather good separation between the red, green and blue basic colors. Combining the information obtained under positive and negative applied bias a colour image is acquired, using the same optical technique either in pinpi´n or in the pini´p configuration, without colour filters or pixel architecture.