Carrier and phonon transport control by domain engineering for high-performance transparent thin film thermoelectric generator

Abstract

We develop transparent epitaxial SnO2 films with low thermal conductivity and high carrier mobility by domain engineering using the substrates with low symmetry: intentional control of the domain size and the defect density between crystal domains. The epitaxial SnO2 films on r-Al2O3 (a low symmetry substrate) exhibit a twice higher mobility than the epitaxial SnO2 films on c-Al2O3 (a high symmetry substrate), resulting in twice larger thermoelectric power factor in the SnO2 films on r-Al2O3. This mobility difference is likely attributed to the defect density between crystal domains. Furthermore, both samples exhibit almost the same thermal conductivities (∼5.1 ± 0.4 W m−1 K−1 for SnO2/r-Al2O3 sample and ∼5.5 ± 1.0 W m−1 K−1 for SnO2/c-Al2O3 sample), because their domain sizes are almost the same. The uni-leg type film thermoelectric power generator composed of the domain-engineered SnO2 film generates the maximum power density of ∼54 μW m−2 at the temperature difference of 20 K. This demonstrates that a transparent film thermoelectric power generator based on the domain engineering is promising to run some internet of things sensors in our human society.