In this letter, the authors develop an optimized Seebeck nanoantenna design suitable for IR harvesting applications. The design is optimized via the so-called particle-swarm-optimization algorithm (PSO), an evolutionary algorithm able to drive the morphology of a nano-object towards an optimum. Along with the so-called nanoloading technique, efforts are subsequently addressed to understand the physical mechanisms behind the wave energy to voltage conversion, from both numerical and theoretical perspectives. In particular, the thermal and intrinsic impedance are considered to be the key issues beneath the device's response.