Abstract
Humidity sensors are indispensable for various electronic systems and instrumentations. To develop a new humidity sensing mechanism is the key for the next generation of sensor technology. In this work, a novel flexible paper-based current humidity sensor is proposed. The developed alternating current electroluminescent devices (ACEL) consist of the electroless plating Ni on filter paper and silver nanowires (AgNWs) as the bottom and upper electrodes, and ZnS:Cu as the phosphor layer, respectively. The proposed humidity sensor is based on ACEL with the paper substrate and the ZnS:Cu phosphor layer as the humidity sensing element. The moisture effect on the optical properties of ACELs has been studied firstly. Then, the processing parameters of the paper-based ACELs such as electroless plated bottom electrode and spin-coated phosphor layer as a function of the humidity-sensitive characteristics are investigated. The sensing mechanism of the proposed sensor has been elucidated based on the analysis. The sensor exhibits an excellent linearity () within the humidity range from 20% to 90% relative humidity (RH) and shows excellent flexibility. We also demonstrate its potential application in postharvest preservation where the EL light is used for preservation and the humidity can be monitored simultaneously through the current.
Highlights
Humidity monitoring is widely applied in the paper industry, tobacco industry, microelectronics, intelligent home, etc
alternating current electroluminescent devices (ACEL), we propose a novel flexible current-type humidity sensor
The and structural and morphological properties of as-received ACELs were examined by scanning electron microscopy (SEM, Hitachi S4800, Tokyo, Japan)
Summary
Humidity monitoring is widely applied in the paper industry, tobacco industry, microelectronics, intelligent home, etc. Filter paper itself is a good sensing element candidate for the detection of gases and humidity due to its high flexibility and inherent porous structure, rough surface which facilitates to absorb the vapors. Paper-based electroluminescent device has been proposed [30] and in most cases the dielectric layer of ACELs is made of barium titanate or some other materials. It was reported that the luminescence of ZnS is influenced by the moisture [31] Inspired by this concept, in this context, based on the detailed study of the effect of humidity on the electrical and optical properties of ACELs, we propose a novel flexible current-type humidity sensor. The humidity was measured through the current change due to the water vapor adsorption by both the filter paper and ZnS:Cu active layer. The humidity sensor based on ACELs provides a new route for humidity detection
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