A low-temperature sintered heterostructure solid film of coordination polymer nanoparticles: an electron-rectifier function based on partially oxidised/reduced conductor phases of Prussian blue

Abstract

Inks of surface-modified nanoparticles (NPs) are a promising fluid for fabricating thin-film electronic devices; however, such NPs are still functionally discrete from each other. Therefore, reconstituting electronic communication among the NPs has been a challenging subject for their nanoscale interfacial assembly. Here, we demonstrate the reconstitution (sintering) ability of surface-modified Prussian blue (PB) and its Ni-replaced analogue (Ni-PBA) NPs that lead to multilayer electronic functions. A double-layer (DL) rigid solid film of the PB (bottom layer) and the Ni-PBA (top layer) NPs has been successfully fabricated on indium-tin-oxide (ITO) substrates by a spin-coating technique using their water inks and a low-temperature sintering process between 120 and 150 °C to immobilise the spin-coated NPs without serious mismatch on the heterostructure DL interface. The DL solid films act as an electron-rectifier device, which is entirely characterised by a PB bottom layer with a minimum nanoscale thickness of ∼20 nm. In the mechanism of the electron-rectifier phenomenon, we reveal the appearance of theoretically predicted partially oxidised/reduced conductor phases of PB.