Utilization of hole trapping effect of aromatic amines to convert polymer semiconductor from ambipolar into n-type

In this study, we added several aromatic amine compounds as dopants to an ambipolar polymer semiconductor, PDBTAZ, and studied the charge transport behavior of the doped polymer thin films in organic thin film transistors. The trap energy (ET), which is the HOMO energy difference between the amine dopant and the polymer, was found related to the hole transport suppression effect of these amines. For an amine with ET < 0.25 eV, at a 2% dopant concentration, little changes in the hole transport characteristics of the doped polymer films were observed. In contrast, for an amine with ET > 0.25 eV, complete hole transport suppression was realized. This study offers a useful approach to converting an ambipolar polymer semiconductor into a unipolar n-type polymer semiconductor.