Ambient-stable, ion-gated poly[N-9′- heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) transistors and phototransistors

Poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) is a low bandgap carbazole-based copolymer, successfully employed in bulk heterojunction solar cells and field-effect transistors. In this work, we report on the possibility to dramatically lower the operating voltage of PCDTBT transistors by using an ion gating medium, instead of conventional gating media, such as SiO2. Using the ionic liquid [EMIM][TFSI] [1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide] as the ion gating medium, we characterized the device performance of [EMIM][TFSI]-gated PCDTBT transistors, in inert atmosphere and in air. Furthermore, we report on [EMIM][TFSI]-gated PCDTBT phototransistors, where the transistor current is not only controlled by the electrical bias applied to the gate electrode but also by exposure to simulated solar light.