Chemical impurity effects on transport in polymer transistors

Exposure of unencapsulated bottom gate polythiophene thin film transistors (TFTs) to several organic and inorganic volatile chemicals induces large changes in the TFT properties. Various neutral molecules cause the mobility of the TFT to decrease and enhance the bias stress effect, with the changes being reversible upon annealing. The effect on the mobility and stress are characteristically different for each compound and are attributed to different preferred locations in the host. Some molecules cause electronic doping of the semiconductor with corresponding changes in threshold voltage. In the case of the donor, ammonia, a gate-induced incorporation rate is observed. The distribution of acceptor energies of the recently found ozone acceptor is analyzed.