Evolution of surface and interface in soluble acene/polymer blends and its critical effects on gas diffusion dynamics in gas sensors

[Display omitted] •TIPS-pentacene thickness in polymer blends altered the gas sensing characteristics.•Adsorption analysis showed similar surface rates but different bulk responses.•10 nm thick TIPS-pentacene exhibited a detection limit as low as 2.6 ppb. Organic field-effect transistor (OFET)-based gas sensors are highly valued for their sensitivity, cost-effectiveness, and operation at room temperature, making them ideal candidates for gas detection applications. For gas sensor performance, gas molecules must not only adsorb onto the organic semiconductor surface but also diffuse into the organic semiconductor-insulator interface that the conductive channel is formed. Therefore, the thickness of the active OSC layer is crucial in determining the efficiency of gas diffusion and the overall sensing response. This study analyzed the impact of semiconductor thin film thickness on gas sensing properties by adjusting the thickness of crystalline organic semiconductors. Using 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), known for its excellent response toward NO2, surface and interface characteristics were modulated through a blend approach. With all other conditions constant, the semiconductor film thickness significantly influenced NO2 detection properties, with the highest sensitivity observed in films around 10 nm thick. A quantitative analysis using Langmuir isotherms demonstrated that reducing the OSC layer thickness from 20 nm to 10 nm could enhance the response speed by a factor of five. Furthermore, the limit of detection (LOD) for TIPS-pentacene films at this reduced thickness was found to be in the low parts per billion (ppb) range.