Title: Fabrication of organic semiconductor based humidity sensor and its environmental applications

Abstract

The compound lophine, 2, 4, 5-triphenyl-1H-imidazole, has been used to fabricate humidity sensors. The sensors were tested in different humidity environments, and at various applied frequencies. The SEM images showed inter-woven spiky needles, pores, pore-channels of diverse shapes and sizes. The H2O molecules interacted with N and NH sites in the aromatic ring of the compound and thus altered the electrical properties due to the imidazole scaffold’s electron acceptor and trifling donating nature. The conduction mechanism is based on Grotthuss hydroxide transfer and prototropic mobility. The calculated dielectric constant of the material was 1.69. In 45-95 %RH limit, the devices capacitance was increased from 11 pF to 460 pF and 7.29 pF to 18.9 pF at applied frequencies 1 kHz and 10 kHz, respectively. The response/recovery time was 39/20 seconds, respectively. The maximum hysteresis was 0.44 % (at 1 kHz) and 1.09 % (at 10 kHz). The R2 values (goodness of fit) 0.98 and 0.99 for chemisorbed and multi-layered physisorbed layers are close to unity and thus considered the best linear-fit. The sensors showed a strong affinity to moisture at ambient conditions with low hysteresis. Fabulous improvement in the device’s sensitivity has been noted over the reported sensitivity of devices based on ceramic materials.