Investigating sensing properties of poly-(dioctylfluorene) based planar sensor

The present paper reports on the fabrication and investigation of a novel poly (9, 9-dioctylfluorene) (F8) based humidity and temperature sensor. A thin film of F8, with a thickness of 230 nm, was drop casted on cleaned glass substrate with pre-patterned silver electrodes to form Ag/F8/Ag planar sensor. Gap between the electrodes was 45 μm. Capacitance and resistance measurements against relative-humidity have been carried out at two different frequencies i.e. 120 Hz and 1 k Hz. The capacitance increases while the resistance decreases by almost 4.06 and 1.27 times the initial value, at 120 Hz and 1 k Hz, respectively. Temperature-dependent investigations reveal that capacitance increases 1.54 times with elevating temperatures. The response and recovery times, which show degree of sensor-efficiency, were recorded as 15 s and 7 s, respectively. The surface morphology and structure of the films have been studied using atomic force microscope (AFM) and X-ray diffraction (XRD). For determination of functional groups within F8, FT-IR spectroscopy has been carried out.