Influence of thermal annealing on a capacitive humidity sensor based on newly synthesized macroporous PBObzT2

In this work, we report on the application of a newly synthesized macroporous polythiophene derivative, benzo[b]thiophene end-capped dioctyloxy-benzene(PBObzT2), in the fabrication of a capacitive humidity sensor. The sensor has been fabricated by spin-coating polymer solution in the gap between pre-deposited aluminum electrodes to form a coplanar Al/PBObzT2/Al capacitive humidity sensor. We have also demonstrated how effectively thermal annealing has improved the physical aspects of the active layer and sensing properties of the sensor. The sensor's capacitance is measured against RH variations at different frequencies. Particularly, at an optimum annealing temperature of 75 °C, the sensor exhibits high sensitivity, fast response and low hysteresis. The hydrophobic nature of the polymer makes it highly appropriate to be used in the humidity sensors.