Investigation of relative humidity-sensing performance of capacitive and resistive type sensor based on TDTBPPNi metalloporphyrin dielectric layer

A quest for a suitable method to fabricate thin films-based humidity sensor with superior sensitivity in their electric response, calls for a selection of an appropriate material and effective fabrication technique. In this paper, organic semiconductor metalloporphyrin (TDTBPPNi) has been utilized to fabricate highly sensitive humidity sensors by using a novel eco-benign microwave-assisted synthetic procedure. Metalloporphyrin (TDTBPPNi) has been later deposited through facile drop-casting technique on the gap (40 μm) between planar metallic aluminium (Al) electrodes to fabricate surface-type capacitive and resistive type relative humidity sensor (Al/TDTBPPNi/Al). The structural and morphological characterizations of humidity sensing layer have been investigated, which indicate amorphous structure and rough globular surface morphology of the thin film, respectively. The relative humidity sensing capacitive and resistive characteristics of the sensor have been monitored in 39–85% relative humidity (%RH) bandwidth. The fabricated sensor under biasing condition of 1 V of applied bias (Vrms) and 200 Hz AC test frequency, exhibits significantly higher sensitivity of ~102.61 pF/%RH and − 333.07 kΩ/%RH in capacitive and resistive mode of operation. The average values of response and reset time of resistive sensor have been estimated to be ~ 35 and ~ 57 s, respectively. The reasons for this achieved sensitivity and response level have also been discussed.