Conjugated polymers with a helical structure have been in rapid development in recent years because of their potential applications in chemical and biological sensors. We demonstrate the fabrication and characterization of helical nanofibrils of block copolymer poly(4-iso-cyano-benzoic acid 5-(2-dimethylamino-ethoxy)-2-nitro-benzylester)- b-poly(3-hexylthiophene) (PPI(-DMAENBA)- b-P3HT) via a transfer-etching method. The density and lateral length of nanofibrils can be facilely controlled by regulating the process conditions, which, in turn, directly determine the electronic property. Organic field effect transistors based on helical nanofibrils were successfully fabricated with the highest mobility of 9.1 × 10 cm/(V s), an on/off ratio of 3.4 × 10, and high bias stability. The helical nanofibrils were proved to be beneficial for obtaining a highly sensitive and selective chemical sensor. And, the transistor based on helical nanofibrils exhibits a relative response of 28.6% to 100 ppb ammonia, which is even much higher than the responses to 1 ppm ammonia for homo poly(3-hexylthiophene) nanofibrils (7%) and block copolymer nanofibrils without helical structure (0.9%). The combination of helical structure with nanofibrils may provide a new strategy to fabricate high-performance chemical sensors suitable for use in environmental monitoring, industrial and agricultural production, health care, and foodsafety.

A phase-separation method has been developed to control the semiconductor thickness and molecular arrangement via the semiconducting/insulating polymer blend system. The thickness of the poly(3-hexylthiophene) film has been regulated from 10.5 ± 1.4 nm down to 1.9 ± 0.8 nm with a favorable self-assembly degree and the mobility ranging from 0.21 to 0.03 cm V s. The ultrathin films show high bias stability and weak decay after 24 days with a bottom-gate configuration. Benefited from a good molecular order, the films have low activation energy and a 2D charge transport profile in semiconductor layers. Moreover, this blending process can be used as a general strategy of thickness control in flexible low-voltage devices and donor-acceptor-conjugated polymers.

Solar-blind deep ultraviolet photodetectors (DUVPDs) based on conventional inorganic ultrawide bandgap semiconductors (UWBS) have shown promising application in various civil and military fields and yet they can hardly be used in wearable optoelectronic devices and systems for lack of mechanical flexibility. In this study, we report a non-UWBS solar-blind DUVPD by designing ultrathin polymer nanofibrils with a virtual ultrawide bandgap, which was obtained by grafting P3HT with PHA via a polymerization process. Optoelectronic analysis reveals that the P3HT-b-PHA nanofibrils are sensitive to DUV light with a wavelength of 254 nm but are virtually blind to both 365 nm and other visible light illuminations. The responsivity is 120 A/W with an external quantum efficiency of up to 49700%, implying a large photoconductive gain in the photoresponse process. The observed solar-blind DUV photoresponse is associated with the resonant mode due to the leakage mode of the ultrathin polymer nanofibrils. Moreover, a flexible image sensor composed of 10 × 10 pixels can also be fabricated to illustrate their capability for image sensing application. These results signify that the present ultrathin P3HT-b-PHA nanofibrils are promising building blocks for assembly of low-cost, flexible, and high-performance solar-blind DUVPDs.

Chemiresistive sensing is one of the most promising technologies for portable and miniaturized chemical sensing, with applications ranging from air quality monitoring to explosive detection and medical diagnostics. Recently, there have been growing efforts in developing microchip based chemical sensors operating at room temperature with high sensitivity, selectivity, spatial and temporal resolution, long‐term stability, and cost‐effectiveness. Here, the engineering of highly performing miniaturized gas sensors consisting of chemiresistive vertical indium phosphide nanowire (NW) arrays is reported for the first time, and their potential for the selective detection of nitrogen dioxide (NO2), a major air pollutant, is demonstrated. By carefully engineering the NW geometry (i.e., diameter and pitch), a superior sensing performance than those previously reported semiconductor‐based NO2 sensors is achieved, obtaining a limit of detection of 3.1 ppb at room temperature, with outstanding selectivity, and long‐term stability. Kinetic analysis and electrical simulation further reveal the array geometry correlated sensing mechanism, providing insights for the design of future NW array‐based devices. These findings indicate that, owing to their unique nanoscale structures, material properties, and CMOS compatible manufacture processes, III‐V compound semiconductor NW arrays present a new and promising chemical sensing platform for development of future high performance, miniaturized on‐chip sensing system.

No abstract