The present invention is directed to a thermoelectric device that includes a plurality of thermoelectric couples positioned between a top plate and a bottom plate, wherein each thermoelectric couple comprises n-type and p-type element assemblies electrically connected in series and thermally connected in parallel. When the device is used for electrical power generation, the efficiency is increased by using semiconductor materials with a high Seebeck coefficient, increasing the distance between the n-type and p-type element assemblies, increasing the length of the electrical conductors/thermal distance between the top and bottom plates, and/or using an insulation plate spaced from the top plate. When the device is used for heating/cooling, the coefficients of performance are increased by using semiconductor materials with a high Seebeck coefficient and/or optimizing the length of the electrical conductors/thermal distance between the top and bottom plates.