Water-gated organic nanowire transistors

We gated both p-type, and n-type, organic nanowire (NW) films with an aqueous electric double layer (EDL) in thin-film transistor (TFT) architectures. For p-type NWs, we used poly(3-hexylthiophene) (P3HT) NWs grown via two different routes. Both can be gated with water, resulting in TFTs with threshold lower than for conventionally cast P3HT films under the same gating conditions. However, TFT drain currents are lower for NWs than for conventional P3HT films, which agrees with similar observations for ‘dry’ gated TFTs. For n-type NWs, we have grown ‘nanobelts’ of poly(benzimidazobenzophenanthroline) (BBL) by a solvent/non-solvent mixing route with later displacement of the solvent, and dispersion in a non-solvent. Water-gating such films initially failed to give an observable drain current. However, BBL nanobelts can be gated with the aprotic solvent acetonitrile, giving high n-type drain currents, which are further increased by adding salt. Remarkably, after first gating BBL NW films with acetonitrile, they can then be gated by water, giving very high drain currents. This behaviour is transient on a timescale of minutes. We believe this observation is caused by a thin protective acetonitrile film remaining on the nanobelt surface.

Figure optionsDownload as PowerPoint slideHighlights
► Both p-type, and n-type, organic NW films can be gated by DI water.
► As p-type NWs works, resulting TFTs have very low threshold voltages; lower than cast P3HT films.
► N-type BBL nanobelts can be gated with an aprotic gate medium (acetonitrile).
► BBL nanobelts can also be gated by water after first conditioning them with acetonitrile.
► BBL nanobelts gated by water display very high drain currents; however this remarkable behaviour is transient on few minutes.