Tribo-thermoelectric and tribovoltaic coupling effect at metal-semiconductor interface

Frictional heating and triboelectrification are ancient and common physical phenomena. Fricting at a semiconductor interface has brought new tribovoltaic effect, while the frictional heating on semiconductor materials is usually unattended. Here, a tribo-thermoelectric and tribovoltaic coupling effect is reported by rubbing a metal on a semiconductor. The friction energy excites electron-hole pairs at the interface to generate a DC current under the built-in electric field. Meanwhile, the friction generated heat and local temperature non-uniformity drives the majority carrier to move from the hot side toward cold side. The results reveal that the direct-current output of the metal-semiconductor triboelectric nanogenerator includes two parts: the stable part by thermoelectric effect and the fluctuant part by tribovoltaic effect. Faster velocity, larger pressure can enhance both the thermo-voltage/current with larger temperature difference and tribo-voltage/current with more frictional energy. Several superposition states of the thermo-voltage/current and tribo-voltage/current have been demonstrated by theoretical and experimental analysis, which are proven to be determined by the direction of the built-in electric field and the majority carriers of semiconductors. This work has not only proposed the multi-physics coupling effect by the combination of friction and semiconductor, but also demonstrated semiconductor interface based multisource energy harvesting.