Humidity sensors based on aluminum phthalocyanine chloride thin films

In present paper, the fabrication and humidity sensing properties of aluminum phthalocyanine chloride (AlPcCl) thin film based sensors have been presented. AlPcCl thin films with nominal thickness of 50–100 nm are deposited on glass substrates between pre-deposited 50 nm thick aluminum electrodes. The gap between the electrodes is 50 μm. It is observed that the sensing mechanism is based on the variation of resistance with change in humidity. For change in relative humidity (RH) from 20% to 92%, the change in resistance is 22.2×102 and 13.3×102 times respectively for the sensors having 50 nm and 100 nm thick AlPcCl films, while the 1 h annealing of these samples at 100 °C results in increase in average sensitivity up to 30% and 40% respectively. The consequence of measuring frequency and absorption–desorption behavior of the humidity sensor are also discussed in detail. It is also observed that annealing results in minimization of hysteresis and reduction of recovery time (τrec) up to 63% and 70% in sensors with 50 nm and 100 nm thick organic film respectively, while the response (τres) time is 10 s for both the sensors.

► Humidity sensors based on AlPcCl are fabricated and investigated.
► Sensing mechanism is based on variation of resistance with change in humidity.
► Annealing results in increase in average sensitivity from 30% to 40% respectively.
► Very fast response and recovery times.
► Reduction in recovery time by 63%–70% as a result of annealing.