Direct current triboelectric cell by sliding an n-type semiconductor on a p-type semiconductor

Triboelectric generators are a type of devices for harvesting mechanical energy by utilizing triboelectric and electrostatic induction effects. When two materials of different electron affinities are brought into contact, electrons transfer across the contacted surfaces owing to triboelectrification. When the two materials are slid against each other with a variation of the contacting surface area, an alternating current is electrostatically induced in the external circuit. In this paper, a novel electric generator, called triboelectric cell, based on sliding friction between n- and p-type doped semiconductors without changing the contacting area is reported. A direct current is generated in the direction of the built-in electric field in the dynamic p-n junction across the contacted surfaces, flowing from the p-semiconductor through the external circuit to the n-semiconductor. The generated currents and voltages are studied through sliding speeds, accelerations, contacting forces, operation temperatures and the geometries of the top electrode. The direct current generation can be attributed to electron-hole pairs generated at the two sliding surfaces, which are then swept out the dynamic junction by the built-in electric field.