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

Abstract

Flexible, thin-film electronic and optoelectronic devices typically involve a trade-off between performance and fabrication cost^1,2,3. 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 complex^5,6 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 Hz^1/2 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.