Organic Thin Film Transistor with Aligned Nanowires/Thin Film Hybrid Channel for Low-Concentration Detection of NH₃ at Room Temperature

An extremely sensitive ammonia (NH 3 ) sensor was developed by using an aligned nanowires/thin film hybrid channel of an organic thin film transistor (OTFT). Conjugated polymer poly(2,5-bis(3-tetradecylthiophen-2yl)thieno(3,2- b )thiophene) (PBTTT-C14) has been used as semiconductor channel that has been fabricated via “floating film transfer method” (FTM). The crystalline fibrillar microstructure within the liquid phase of the polymer has been developed by mixed solvent, which has been self-assembled on the air–liquid interface through the FTM method. This hybrid structured film was then transferred on a cleaned Si/SiO 2 substrate, whereas Au was used as source–drain electrodes of this OTFT. To investigate the ammonia sensing behavior of the designed OTFT, various low concentrations of the NH 3 have been exposed on the channel ranging from 0.2 to 5 ppm. From the accumulation mode drain current variation, it was observed that the sensor is extremely sensitive toward ammonia gas with a response of about 75% at 5 ppm, whereas the limit of detection (LOD) is ∼0.67 ppm, which confirms its applicability at the lower concentrations. More interestingly, the depletion mode current of this OTFT reduces ∼200 times during this investigation, which is ∼40 times larger variation than the accumulation mode current. Additionally, these current variations of this sensor have excellent linearity to the NH 3 concentration. This fabricated sensor also exhibits excellent selectivity and sensitivity to NH 3 gas, which can satisfy the requirements for real-world applications.