Atmospheric Dependence of Thermoelectric Generation in SnO2 Thin Films with Different Intergranular Potential Barriers Utilized for Self-Powered H2S Sensor Fabrication

The profound contribution of grain boundaries to the Seebeck voltage generation in the polycrystalline semiconductors has recently been stated. Considering the direct link between the chemiresistive sensitivity and intergranular energy barrier, the “chemithermoelectric” (CTE) effect follows as the interrelating effect. Here, we compare the magnitude of the CTE effects in SnO 2 thin films with different intergranular potential barriers and show that the Seebeck coefficient and CTE magnitude are both linearly related to the experimentally determined charge conduction barrier height. It is shown that exposing the samples to the H 2 S-contaminated air at elevated temperatures reversibly modifies the barrier height and, hence, the Seebeck voltage generated along the sample at the presence of a constant temperature gradient. The demonstrated effect is utilized for the fabrication of the first CTE-based H 2 S sensor. Safety regulations regarding this highly hazardous gas are tight and the presented device provides safer monitoring of the surrounds than its chemiresistive counterpart; natural aging brings its output closer to the alarming level preventing silent failure. Powered by a temperature gradient, the device detects the presence of sub-parts per million H 2 S concentrations in air requiring no electrical power source for operation.