Sensitive solution-processed visible-wavelength photodetectors

One billion image sensors worldwide render optical images as digital photographs in video cameras, still cameras and camera phones. These silicon-based sensors monolithically integrate photodetection with electronic readout. However, silicon photodiodes rely on a smaller bandgap than that required for visible detection; this degrades visible-wavelength sensitivity and produces unwanted infrared sensitivity. Thin-film top-surface visible photodetectors have therefore been investigated based on amorphous(1), organic(2) and colloidal quantum-dot(3) semiconductors. However, none of these devices has exhibited visible sensitivity approaching that of silicon. Here we report a sensitive solution-processed photodetector that, across the entire visible spectrum, exhibits D* (normalized detectivity) greater than 5 3 1012 Jones (a unit of detectivity equivalent to cm Hz(1/2)W(-1)). A photoconductive gain of > 100 has been measured, facilitating high-fidelity electronic readout, and the linear dynamic range is greater than 60 dB, as required for high-contrast applications. These photodetectors are also compatible with flexible organic-based electronics.