Capacitive and resistive type bi-modal relative humidity sensor based on 5,10,15,20-tetraphenylporphyrinatonickel (II) (TPPNi) zinc oxide (ZnO) nanocomposite
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Date
2021
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UMT, Lahore
Abstract
The selection of the appropriate sensing material and efficient manufacturing methodology is needed to develop an acceptable approach for the production of thin film-based moisture sensors with better electronic sensitivities. Organic semiconductors and their nano-composite have the potential for relative humidity sensing applications since they have a controllable pore size, a broad variety of manufacturing methods, ease of fabrication, and low cost The use of organic semiconductor 5,10,15,20-tetraphenylporphyrinatonickel (II) (TPPNi) – Zinc Oxide (ZnO) nanocomposite (TPPNi-ZnO) to build ultra-sensitive humidity sensors has been studied in this work utilizing a unique eco-friendly microwave-assisted synthesis method. The organic semiconductor (5,10,15,20-tetraphenylporphyrinatonickel (II) (TPPNi)) and metal oxide (Zinc Oxide (ZnO)) has been synthesized separately and deposited through facile drop-casting technique on the separation (40 μm) between the pair of aluminum (Al) electrodes. The metallic electrode thus formed a surface type resistive and capacitive type humidity sensor (Al/TPPNi-ZnO/Al). The photophysical properties of humidity sensing active layer (TPPNi - ZnO) has been studied by using UV–vis absorption spectroscopy and the structural and morphological has been examined by XRD and FESEM, which shows amorphous structure and rough globular surface morphology of the active surface thin film. The relative humidity sensing capacitive and resistive characteristics of the humidity sensor have been explored by exposing it to various wide range relative humidity (%RH) levels (40 - 85 %RH). The fabricated sensor under biasing condition of 1V of applied bias (Vrms) and 500 Hz AC test frequency, exhibits significantly higher sensitivity of ~ 387.03 pF/%RH and 95.79 kΩ/%RH in capacitive and resistive mode of operation. The average response time and recovery time of this resistive sensor have evaluated to be ~ 30 s, each. The reasons of this achieved sensitivity and response level has also been discussed.