Amorphous Si/SiC stacked photodiodes working as photonic devices are reviewed. Several applications (imagers, wavelength division demultiplexing devices and optical amplifiers) are proposed. In the imagers scans speeds up to 10 K lines per second were achieved without degradation in resolution. In the Wavelength Division Demultiplexing devices transmission rates are of the order of 4 kbit/s. Optical amplification occurs under steady state irradiation where the polychromatic mixture of different colors is higher than the sum of the individual monochromatic contributions. Electrical models are present to support the sensing methodologies. Experimental and simulated results show that the tandem devices act as charge transfer systems. They filter, amplify, store and transport the photogenerated carriers, keeping its memory (colour, intensity and bit rate) without adding any optical pre-amplifier or optical filter as in the standard p-i-n cells.