Band-like transport, high electron mobility and high photoconductivity in all-inorganic nanocrystal arrays

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Abstract
Flexible, thin-film electronic and optoelectronic devices typically involve a trade-off between performance and fabrication cost1,2,3. For example, solution-based deposition allows semiconductors to be patterned onto large-area substrates to make solar cells and displays, but the electron mobility in solution-deposited semiconductor layers is much lower than in semiconductors grown at high temperatures from the gas phase4. Here, we report band-like electron transport in arrays of colloidal cadmium selenide nanocrystals capped with the molecular metal chalcogenide complex5,6 In2Se42−, and measure electron mobilities as high as 16 cm2 V−1 s−1, which is about an order of magnitude higher than in the best solution-processed organic7 and nanocrystal8 devices so far. We also use CdSe/CdS core–shell nanoparticles with In2Se42− ligands to build photodetectors with normalized detectivity D* > 1 × 1013 Jones (I Jones = 1 cm Hz1/2 W−1), which is a record for II–VI nanocrystals. Our approach does not require high processing temperatures, and can be extended to different nanocrystals and inorganic surface ligands.