This paper systematically compares the gas sensing properties of organic field‐effect transistors (OFETs) based on patterned 5,11‐bis(triethylsilylethynyl)anthradithiophene (TES‐ADT) films, by adopting TES‐ADT crystal arrays of various shapes and dimensions. The patterning and crystallization of spin‐cast TES‐ADT layers are achieved by the use of a solvent‐containing engraved polydimethylsiloxane (PDMS) mold. Decreasing width of the TES‐ADT pattern enhances gas sensing performance, as well as field‐effect mobility of OFETs. The decreased grain boundary density at narrower line width contributes to the increase of field‐effect mobility. On the other hand, the increased sensing performance is mainly due to the increased area of crystal edges, which provides a diffusion pathway for gas molecules to arrive at the semiconductor‐dielectric interface. This study provides new perspectives on the diffusion pathway of gas molecules in OFET‐based gas sensor, and will be useful for the design of active channel to boost the gas sensing properties of OFETs.

sensors is governed significantly by the film morphology. [7][8][9] Therefore, strategic approaches to ameliorate the sensitivity of FET-based gas sensors have been centered on the morphological optimization of the OSC layer, such as increase of the diffusion or the contact area of the gas molecules and control of the OSC-dielectric interfacial properties. [10][11][12] In addition, ultrathin film and nano/micro-structured OSCs have been utilized as FET active layers, to improve the response rate of FET sensors to target analytes. [13] In particular, as crystallinity and molecular assembly of OSCs can be easily tuned by modifying the structure of the conjugated frameworks, various polymeric OSCs have been actively studied for FET-based gas sensors. [14][15][16] Although deconvoluting the individual effects of chemical structure and morphology on the detection sensitivity of FET-based gas sensors is challenging, development of effective structures that cause significant changes in carrier density through strong interaction with the analytes is inevitable to further improve the performance of such sensors.Nitrogen dioxide (NO 2 ) is a detrimental exhaust gas abundantly released into the atmosphere from industrial sources. It is toxic and, particularly dangerous gases because of its strong oxidizing power that makes it highly reactive. Moreover, since human respiration system can be fatally damaged when exposed to low concentrations of NO 2 in closed work-spaces, health and safety agencies strongly suggest a limit of exposure of 5 ppm of NO 2 for longer than 15 min. [17] Therefore, the precise, sensitive, and efficient detection of NO 2 is of the outmost importance for human health and disease prevention. In FET-based NO 2 sensors typically utilizing a p-type OSC as an active layer, the detection and sensitivity mechanisms generally follow hole carrier generation via charge transfer interaction with electron-accepting NO 2 . [18,19] This implies that the electron-donating properties of the p-type OSC are interconnected with the NO 2 detection ability of the FET sensors. The OSC with higher electron-donating ability would be beneficial to improve the detection sensitivity to NO 2 . In this contribution, three conjugated polymers (CPs, polymeric OSCs) are designed, which share the same indolocarbazole-based conjugated framework considered as known to a good electron donor. [20] In addition, to compare the effect of the morphology on NO 2 detection, different side chains were used to modulate Three conjugated polymers (CPs) containing indolocarbazole-based similar conjugated frameworks are designed to investigate the NO 2 detection capability of field-effect transistor (FET) sensors. The partly linear aliphatic side chain strengthens the crystallization tendency of the CPs, but the crystallinity is critically degraded when introducing an ethylene oxide (EO)modified side chain to the same conjugated framework. Although the highly crystalline morphology of the CP helps to achieve high hole mobility, the NO 2 response rate...

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The correlations between semiconductor type and gas sensing properties in soluble acene/polymer blends have not yet been examined. Here, the phase separation mechanism in pseudo‐liquid phase blend film is investigated and an unusual solid‐state morphology that is effective for amperometric gas sensing performance is demonstrated. In 6,13‐bis(triisopropylsilylethynyl) pentacene (TIPS–pentacene)/poly(fluorine‐co‐triarylamine) (PTAA) blend, two phases are uniformly mixed, without being completely phase‐separated due to the similar solubility and surface tension. On the other hand, in 2,8‐difluoro‐5,11‐bis(triethylsilylethynyl) anthradithiophene (diF–TES ADT)/PTAA blend, the diF−TES ADT molecules are segregated both at the air–film, and film–substrate interfaces, and subsequently crystallized with a high degree of crystal perfection. In the meanwhile, Marangoni‐flow induces crater‐like via hole structure of PTAA at the middle layer. In situ measurement of (ultraviolet–visible) UV–vis absorption spectra and computational calculation reveal kinetics of liquid–solid–crystal transition in relation to the functional groups of soluble acene. Interestingly, flow driven hole structure of PTAA in diF–TES ADT/PTAA blend film allows the target NO2 gas to selectively penetrate the channel region, thereby enhancing sensitivity toward NO2, while decreasing affinity with other gases. The results provide protocols for fabricating highlperformance field‐effect transistors and gas sensors in a blending system.