Humidity sensing properties of Cu₂O-PEPC nanocomposite films

Abstract

A blend of copper oxide nanopowder (Cu 2 O), 3 wt.%, and poly-N-epoxypropylcarbazole (PEPC), 2 wt.%, in benzol was drop-casted on glass substrates with pre-deposited surface-type silver electrodes for the fabrication of Cu 2 O-PEPC nanocomposite thin films. The thicknesses of the Cu 2 O-PEPC films were in the range of 10-13 m. The effect of humidity on the electrical properties of the nanocomposite films was investigated by measuring the capacitance and dissipation of the samples at two different frequencies of the applied voltage: 120 Hz and 1 kHz. The AC resistance of the samples was determined from the dissipation values, and the DC resistance was measured directly. The effect of ageing on the humidity sensing properties of the nanocomposite was observed. After ageing, it was observed that at 120 Hz and 1 kHz, under a humidity of up to 86% RH, the capacitance of the cell increased by 85 and 8 times, and the resistance decreased by 345 and 157 times, accordingly, with respect to 30% RH conditions. It was found that with an increase in frequency, the capacitance and resistance of the samples decreased. It is assumed that the humidity response of the cell is associated with the diffusion of water vapors and doping of the semiconductor nanocomposite by water molecules.

A Humidity Sensing Organic-Inorganic Composite for Environmental Monitoring

“…The humidity sensing capability of a blend of Cu 2 O and PEPC has been investigated in our previous study and the bandwidth of the sensor was found to be 36-86% RH, whilst its sensitivity was found to be 0.83 pF/%RH [3]. The humidity sensing capability of NiPc has also been investigated earlier by Shah et al [1] who reported a nonlinear increase in capacitance value with increasing humidity level from 35% to 90% RH, while the sensitivity was reported to be 8.93 pF/%RH. Keeping in mind the potential of NiPc and PEPC for humidity sensors, we have investigated a film of organic-inorganic composite of PEPC, NiPC and Cu 2 O as humidity sensor, where Cu 2 O is used as template to enhance the surface roughness.…”

“…These features give organic semiconductors an economic and technological edge over conventional inorganic semiconductor sensing materials. Consequently, extensive R&D efforts have been directed towards various organic semiconductors and their composites to identify appropriate materials for humidity sensing applications [1–5]. A good sensing material must meet certain stringent requirements such as high sensitivity, reproducibility, fast response and recovery time, small hysteresis, low power consumption and portability, along with durability and long lifetime [6].…”

“…Due to the formation of the PEPC-NiPc complexs the resistance of the composite also decreases, that allows the capacitance of the humidity sensor to increase. The purpose of this study is to tune the sensitivity, bandwidth and linearity in response characteristics of the humidity sensor, with the aim of increasing the sensitivity of the previously reported humidity sensors using PEPC and NiPc [1,15,16], which has been successfully achieved.…”

Organic Thin‐Film Capacitive and Resistive Humidity Sensors: A Focus Review

“…Karimov et al have reported on the characterization of humidity sensors based on copper oxide nanoparticles and poly‐ N ‐epoxypropylcarbazole (Cu 2 O–PEPC) nanocomposite films. They studied the capacitive and electrical dissipation responses of the Cu 2 O–PEPC hybrid system toward the change of RH and have performed under operating frequencies of 120 Hz and 1 kHz and under applied voltage.…”

“…b) Resistance–relative humidity (RH) relationships of the Ag/Cu 2 O–PEPC/Ag device measured at 1) DC, 2) 120 Hz, and 3) 1 kHz of the applied voltage. Reproduced with permission . Copyright 2012, IOP Publishing Ltd.…”