Surface chemistry mediates thermal transport in three-dimensional nanocrystal arrays

Arrays of ligand-stabilized colloidal nanocrystals with size-tunable electronic structure are promising alternatives to single-crystal semiconductors in electronic, optoelectronic and energy-related applications1–5. Hard/soft interfaces in these nanocrystal arrays (NCAs) create a complex and uncharted vibrational landscape for thermal energy transport that will in-fluence their technological feasibility. Here, we present thermal conductivity measurements of NCAs (CdSe, PbS, PbSe, PbTe, Fe3O4 and Au) and reveal that energy transport is mediated by the density and chemistry of the organic/inorganic interfaces, and the volume fractions of nanocrystal cores and surface ligands. NCA thermal conductivities are controllable within the range 0.1–0.3 W m−1 K−1, and only weakly depend on the thermal conductivity of the inorganic core material. This range is 1,000 times lower than the thermal conductivity of sili