Capacitive-resistive measurements of cobalt-phthalocyanine organic humidity sensors

Abstract

Abstract:In this study, the fabrication and characterization of capacitive humidity sensors using cobalt-phthalocyanine (CoPc) as the active material were presented. Thin films of CoPc were deposited by drop casting on glass substrates with pre-deposited aluminum electrodes to form Al/CoPc/Al surface-type humidity sensors. The effect of humidity on the electrical properties of the CoPc film was investigated by measuring capacitance and resistance of the samples at four different frequencies of the applied voltage. It was observed that the capacitance of the sensor increased while the resistance decreased with raising the relative humidity. It was also found that the values of capacitance and resistance decreased with increasing frequency. The optical absorption spectra and optical band gap energy of CoPc films were measured. The structure of CoPc powder and thin films has been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Results of XRD studies show that the film structure is polycrystalline with the monoclinic structure while thin films have a peak for annealing temperatures with (100) orientation. Also, the surface morphology (grain size and roughness) for CoPc films have been studied by AFM.

Structural and Surface Morphology Analysis of Copper Phthalocyanine Thin Film Prepared by Pulsed Laser Deposition and Thermal Evaporation Techniques

“…Phthalocyanine is a generally P-type semiconductor, thermally stable and can easily be sublimated as thin films with high quality. Phthalocyanine has been found application as semiconducting devices, organic field effect transistor OFET [1], organic humidity sensors [2], photovoltaic cells, rectifying devices, liquid crystal displays and gas sensors. The electrical, optical and structural properties of Pc thin films are dependent on various parameters such as evaporation rate, substrate temperature and annealing temperature [3].…”

Hybrid Bilayer Heterojunction Al/ZnPc/ZnO /ITO Thin Films Solar Cell Prepared by Pulsed Laser Deposition

“…Low mobility is a significant disadvantage for organic semiconductors compared to inorganic semiconductors [7]. Zinc Phthalocyanine (ZnPc) is the most used organic compounds as an effective layer in photovoltaic solar cells (PSCs) owing to its multiple maximum absorptions in the visible part of the solar spectrum (less than 700 nm) [8][9][10]. ZnO was the most frequently used as electron transport layer (ETL) products for inverted solar cells owing to the elevated optical transparency in the visible and near-infrared area, as well as the elevated mobility of carriers [11].…”