In this thesis, the possibility of a humidity sensor based on conducting polymer polyaniline (PANI) doped with a novel organic dopant, sulfosuccinate acid (SSA), is explored. PANI-SSA-based resistive sensors show considerably high humidity sensitivity of 1.70%/%RH, with a limit of detection (LOD) value of 8.046%RH, and linearity covering a wide range of relative humidity (RH) from 18% to 80%. The molar ratio of PANI: SSA is varied to get optimum sensing response at around a 1:2 ratio. The origin of the sensing response is attributed to the adsorption of water molecules at the surface of PANI-SSA films, leading to the lowering of activation energy for electron hopping.

The latter part of this thesis includes two all-organic device structures for humidity sensing: one is based on a metal-insulator-metal (MIM) capacitor and the other is based on a metal-insulator-semiconductor (MIS) capacitor using PANI-SSA as a humidity-sensitive conducting layer in both the structures. A noticeable increase in capacitance upon exposure to humidity in MIM-based device structure resulted in a sensitivity of 2.97%/ %RH, LOD of 0.591%, and linearity covering 0% to 90%RH. In MIS capacitor-based devices, the entire capacitance-voltage (C-V) characteristic was observed to shift upon exposure to humidity. In addition, a change in C-V characteristics with respect to the humidity level in the moderate accumulation regime can offer another degree of freedom in humidity measurement.