No abstract

For next-generation gas sensors, conductive polymers have strong potential for overcoming the existing deficiencies of conventional inorganic sensors based on metallic oxides. However, the signal of organic gas sensors is inferior to that of inorganic metal oxide gas sensors because of organic gas sensors’ poor charge carrier transport. Herein, the combination of an organic transistor-type gas sensor and a zeolite with strong gas-adsorbing properties is proposed and experimentally demonstrated. Among the various investigated zeolites, ZSM-5 with ∼5.5 Å pore openings enhanced the adsorption for small gas molecules when combined with a polymer active layer, where it provided a pathway for gas molecules to penetrate the zeolite channels. Moreover, nitrided ZSM-5 (N-ZSM-5) enhanced the sensing performance of NO2 molecules selectively because N in the N-ZSM-5 framework strongly interacted with NO2 molecules. These results open the possibility for zeolite-modified organic gas sensors that selectively adsorb target gas molecules via heteroatoms substituted into the zeolite framework.

Spin-cast small π-conjugated molecules exhibit poor molecular order because of rapid evaporation of the solvent, resulting in low charge-carrier mobility. Herein, we present simple ultraviolet (UV) exposure methods as a versatile post-treatment for inducing the growth of crystalline spherulites of 6,13-bis-(triisopropylsilylethynyl)pentacene (TIPS-PEN). The UV exposure effectively transformed the amorphous state into a crystalline phase in the solid films. UV exposure of the TIPS-PEN films spincast using toluene with a high boiling point improved the intermolecular interaction within only a few minutes, which enhanced charge-carrier transport in organic transistors prepared using these films. The presence of residual solvent facilitated the mobilization of TIPS-PEN molecules, enabling their reorganization. Furthermore, UV exposure of the patterned specific regions in TIPS-PEN films reduced the off-state currents in the organic transistors prepared using the films.