Dielectric Study of Cost-Effective, Eco-Friendly PVA-Glycerol Matrices with AgNW Electrodes for Transparent Flexible Humidity Sensors

In this work, a deep insight is given into the dielectric properties and the humidity response of flexible polymer matrices, composed of polyvinyl alcohol (PVA) and glycerol (Gly), using silver nanowire networks as transparent electrodes (AgNW TE). These electrodes, known for their high electrical conductivity, optical transparency, and excellent flexibility, are deposited here by open-air, scalable spray coating technique. Analysis of the dielectric constant epsilon ' and loss tangent tan delta according to the density of the AgNWs shows that the latter do not cover the entire surface with PVA and induces an interfacial polarization effect. Wide frequency range of impedance spectroscopy (1 Hz to 1 MHz) on both, PVA-Gly samples with AgNW TE (4 omega sq(-1)) networks electrodes and sputtered silver electrodes (Ag bulk el), reveal no significant change in epsilon ' and tan delta. Finally, the humidity sensing properties of PVA-Gly exhibit good response between 20% to 90% humidity range and low hysteresis. This is related to the non-continuous structure of AgNW TE. At 100 Hz, the PVA-10 wt% Gly presents high sensitivity of 0.08 nF/% RH with an hysteresis value of about 1.5% at 70% RH. These results indicate that AgNW networks show great potential for integration in transparent and flexible humidity sensors.