Discovery of a New Odour Sensing Mechanism Using an n-Type Organic Transistor

For the first time, we have demonstrated an n-type organic thin film transistor (OTFT) odour sensor. A systematic comparison of a PDI8-CN2 n-type OTFT with an otherwise identical p-type OTFT reveals significant differences between their responses under octylamine odours. While the p-type OTFT displays the common decrease of saturated drain current, the observed drain current in the n-type OTFT increases significantly. We find both, an increase in carrier mobility, and off-current, under exposure. This is consistently explained by reductive doping of the n-type semiconductor with the Lewis base, octylamine. Since this is uniquely accessible to n-type organic semiconductors, we open up a new interaction window for OTFT odour sensing. The increase of drain current will make Lewis bases stand out from interferants. The observation of doping in an n-type organic semiconductor may be the first step towards n-type synthetic metals, mirroring the common synthetic metals, which use doped p-type organic semiconductors.