Disclosed is a foil segment for a thermoelectric generator comprising a top plate disposed in spaced relation above a bottom plate. An array of the foil segments is perpendicularly disposed in side-by-side arrangement between and in thermal contact with the bottom and top plates. Each foil segment comprises a substrate having a thickness of about 7.5-50 microns, opposing front and back substrate surfaces and a series of spaced alternating n-type and p-type thermoelectric legs disposed in parallel arrangement on the front substrate surface. Each of the n-type and p-type legs is formed of a bismuth telluride-based thermoelectric material having a thickness of about 5-100 microns, a width of about 10-100 microns and a length of about 100-500 microns. The alternating n-type and p-type thermoelectric legs are electrically connected in series and thermally connected in parallel such that a temperature differential between the bottom and top plates results in the generation of power.