Near-infrared imaging with quantum-dot-sensitized organic photodiodes

Solution-processed photodiodes with infrared sensitivities at wavelengths beyond the bandgap of silicon (corresponding to a wavelength of similar to 1,100 nm) would be a significant advance towards cost-effective imaging. Colloidal quantum dots are highly suitable as infrared absorbers for photodetection, but high quantum yields have only been reported with photoconductors(1-3). For imaging, photodiodes are required to ensure low-power operation and compatibility to active matrix backplanes(4). Organic bulk heterojunctions(5) are attractive as solution-processable diodes, but are limited to use in the visible spectrum. Here, we report the fabrication and application of hybrid bulk heterojunction photodiodes containing PbS nanocrystalline quantum dots as sensitizers for near-infrared detection up to 1.8 mu m, with rectification ratios of similar to 6,000, minimum lifetimes of one year and external quantum efficiencies of up to 51%. By integration of the solution-processed devices on amorphous silicon active matrix backplanes, we demonstrate for the first time near-infrared imaging with organic/inorganic hybrid photodiodes.