Solution-Processed Ultrathin Semiconductor Films for High-Performance Ammonia Sensors

A high-performance ammonia sensor based on a donor-acceptor conjugated polymer, bithiophene and bis(2-oxoindolin-3-ylidene)-benzodifuran-dione (PBIBDF-BT), is designed and fabricated. To improve its sensing performance, a polymer semiconductor ultrathin film with a minimum thickness of approximate to 4 nm is prepared using a phase separation method. The relationship between the ammonia sensing performance and film thickness is systematically studied. The ammonia sensor based on an ultrathin film shows a high sensitivity (S = 953) and a response time of less than one second (T-res = 0.63 +/- 0.11 s). The preparation of ultrathin film sensors by the phase separation method not only expands the existing preparation methods of ammonia gas sensors but also provides a simple and effective design strategy for the fabrication of rapid-response gas detection sensors in the future. In addition, the advantage of the solution phase separation method to control the thickness of the ultrathin film helps to understand the gas sensing mechanism and the sensing behavior of ultrathin film devices.