Abstract
•A newly phthalocyanine derivative has been successfully fabricated and utilized as an organic humidity sensor.•Effects of spin coating rate on the wettability of the active layer are studied.•The thinnest active layer film exhibits high sensitivity, fast recovery time and low hysteresis.
The effect of various active layer thicknesses (approximately 66, 80 and 90 nm) was studied on the electrical properties of a vanadyl 3,10,17,24-tetra-tert-butyl-1,8,15,22-tetrakis(dimethylamino)-29H,31H-phthalocyanine (VTP)-based capacitive humidity sensor. Along with that, characterization of the structural and film wettability are being sought to ensure that the mechanism of humidity sensing properties in the sensor is well understood, allowing a controlled production situation to be established. Using the solution processed spin coating, the sensor devices have been fabricated in the planar geometry of Al/VTP/Al, with the capacitance as a function of relative humidity levels of 1 V input. In the present study, the device with the thinnest (66 nm) VTP film has been shown to possess optimized performance with a maximum sensitivity of 9.2 pf/%RH at 500 Hz than that of thicker (80 and 90 nm) VTP films. The sensitivity of the VTP-based sensor with the thickness of approximately 80 and 90 nm are reduced to 7.7 pf/%RH and 2.55 pf/%RH, respectively.