Development of highly sensitive relative humidity sensor based on nanoporous PCPDTBT thin film

A novel type of capacitive humidity sensor with surface-type electrode geometry is presented in the present study. The high sensitivity and significantly high bandwidth associated with this planar-type humidity sensor (Al/PCPDTBT/Al) allow the facile and reliable estimation of ambient humidity. The...

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Bibliographic Details
Published in:	Synthetic metals Vol. 298; p. 117429
Main Authors:	Shafiq, Foqia, Qadir, Rupak Wasman, Qadir, Karwan Wasman, Zafar, Qayyum
Format:	Journal Article
Language:	English
Published:	Elsevier B.V 01-09-2023
Subjects:	Capacitive and resistive type Hierarchical nanoporous surface morphology Humidity sensors Response and recovery time Hierarchical nanoporous surface morphology Response and recovery time Capacitive and resistive type Humidity sensors
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Summary:	A novel type of capacitive humidity sensor with surface-type electrode geometry is presented in the present study. The high sensitivity and significantly high bandwidth associated with this planar-type humidity sensor (Al/PCPDTBT/Al) allow the facile and reliable estimation of ambient humidity. The use of a polymer sensing material Poly[2,6-(4,4-bis-(2-ethylhexyl)− 4 H-cyclopenta[2,1-b;3,4-b՛]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) with hierarchical nanoporous surface morphology and large surface/volume ratio ensures the sensor’s stable performance coupled with swift response to ambient humidity changes. Specifically, at a relatively lower frequency bias signal (i.e., 1 kHz), a fairly higher order of humidity sensitivity has been observed, i.e., 415.07 pF/%RH. While, sensitivities at significantly higher AC signal frequencies (i.e., 10 and 100 kHz) have been experimentally determined to be 345.18 pF/%RH and 154.72 pF/%RH, respectively. Likewise, the resistive sensitivity of the humidity sensor has been estimated to be − 3624.88 kΩ/%RH, − 2381.11 kΩ/%RH and − 1338.14 kΩ/%RH, at 1, 10 and 100 kHz test frequencies, respectively. The operating mechanism of the capacitive humidity sensor relies on an increase in the dielectric constant of the PCPDTBT active sensing layer accompanied by the rise in the ambient humidity levels. In addition to enhanced bandwidth and improved capacitive and resistive sensitivity, the mean response & recovery time of the fabricated device have been recorded to be ∼ 4 min, 17 s and ∼8 min, 43 s, respectively. •A solution-processed humidity sensor using moisture-sensitive PCPDTBT polymer has been presented.•PCPDTBT has been strategically selected because of its high stability and easy solubility in a wide range of organic solvents.•The hierarchical nanoporous surface morphology ensures the sensor’s swift response to ambient humidity changes.•Specifically, at 1 kHz bias signal, a fairly higher order of humidity sensitivity has been observed, i.e., 415.07 pF/%RH.•The mean response & recovery time of the sensor have been recorded to be ~4 min, 17 sec and ~8 min, 43 sec, respectively.
ISSN:	0379-6779 1879-3290
DOI:	10.1016/j.synthmet.2023.117429