In the present work, through the use of the COMSOL Multiphysics software, thermocouples (TCs), constituted by a p and a n type leg, and thermoelectric (TE) devices with different geometries are numerically simulated aiming for an optimized geometry. The semiconductor material used in the simulation is bismuth telluride (Bi₂Te₃) and copper (Cu) is used to achieve the electrical contact between the TE pillars. Two geometries of the thermocouple legs are studied, cubic and cylindrical geometries, revealing that both present identical performances under the same conditions. From these simulations, the optimal ratios achieved between the various geometrical parameters of the TC’s are analysed. It was verified that it exists an optimal ratio between the height and the width of the TE legs with the value 5 × 10⁻³. Moreover, it is shown that increasing the cross-section area of the legs enhances the power produced by a TC. It was also observed that the length of the copper contacts should be smaller than 0.05 times the width of the TE legs for the best performance to be achieved. It was also established that there is an optimal ratio between the copper contacts height and the TE legs height, being, approximately, 40. For a TE device, an increase in the number of TC’s is favourable towards a better performance.