A planar thermoelectric generator (TEG) could be used as an energy harvester for wireless sensor networks (WSNs). Its planar configuration offers the advantages of miniaturization and low-cost fabrication. Herein, we report the fabrication of a device based on a co-evaporated thick film of Bi-Te. Before fabrication we studied quantitative optimization dimensions for the planar TEG via finite element method (FEM) simulations. The planar TEG was also used in a high-performance solar thermoelectric generator (STEG) that concentrated heat from solar radiation via a solar absorber to generate a temperature difference (Delta T) between two thermoelectric and electrode junctions. When exposed to a solar simulator, the STEG produced a Delta T of about 6 degrees C and generated 2.3 mu W of power. The demonstrated high flexibility and mechanical stability of this device suggests applications in wearable electronics.