Organic gas sensors possess many advantages over the traditional inorganic metal oxide-based gas sensors in many aspects like room temperature sensing, flexibility, etc. Understanding the sensing mechanism in chemiresistor and OFET based sensing devices is one of the keys to achieving better performances. Inspite of tremendous achievements in this field, the proper understanding of sensing mechanism still lacks behind especially in establishing the relationship between device performance and intrinsic charge transport properties of organic semiconductors (OSC) which is fundamentally different from usual inorganic ones. In this work, we designed a small organic molecule with push-pull architecture, trans-4-nitro-4' -dimethylamino- α -aminostilbene (NNDMNH2 ) which predicted to have one-dimensional (1D) π - π stacking of molecule, the primary building block of the organic nanowire, nanofiber, etc. Inspired by the fact that, these types of nanostructure have been used to study the fundamental properties of OSC, we used NNDMNH2 nanowire as a prototype to study the correlation between the sensing mechanism and basic charge transport parameters. Our work shows how possibly the modulation of coupling matrix element, one of the basic charge transport parameter, due to change in molecular geometry during adsorption of gas molecules (non-local electron-phonon coupling) can decrease the intrinsic mobility and ultimately effects the sensing performance of the device. Based on our findings we proposed a materials design principle that may help to achieve better performance in the future. We also find NNDMNH2 as a potential sensor of oxidizing SOx (x =2,3) gases, which is important from the fact that OSC based gas sensors are still far behind from its inorganic counterpart in sensing oxidizing gases.

Correlating charge transport properties with gas sensing mechanism in organic nanowires: NNDMNH2 as a prototype

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.