Tuning the Morphology of Isoindigo Donor–Acceptor Polymer Film for High Sensitivity Ammonia Sensor

Monitoring the ammonia gas is of great interest to both environmental benefits and human health. The recent advance in polymer thin film transistors (TFTs) can realize high sensitivity and low‐cost gas sensors. Ammonia gas interacts with charge carrier channels and polymer/dielectrics interface through Coulomb force. This is the first report of high sensitivity and reusable ammonia sensor fabricated from thiophene‐isoindigo donor–acceptor conducting polymer. This kind of polymer has advantages of simple synthesis and excellent air stability. The systematic study is carried out to investigate relationship among chemical structure variation and morphology control of polymer to the performance of ammonia sensor. High crystallinity, favored crystal orientation, and direct percolation routes for analytes are found to be essential to increase the susceptibility of polymers to ammonia gas. By strengthening edge‐on morphology, the sensitivity can be enhanced fivefold for the same polymer. The idea can put forward the development of sensor array in a time‐efficient manner by employing the morphology effect. The first high sensitivity ammonia sensor based on isoindigo donor–acceptor conducting polymer is successfully developed. The air stable polymers can be synthesized easily and fabricated into sensor by simple spin‐coating. Controlling crystallinity and morphology are crucial to achieve high sensitivity. A detection limit of 1 ppm is achieved by strengthening the edge‐on morphology of thin film in transistor.