Passive electricity generation via radiative cooling, combined with thermoelectric generators, is garnering global attention for its potential to mitigate environmental pollution and greenhouse gas emissions associated with fossil fuel-based power generation. However, optimizing radiative cooling and thermoelectric generator systems often encounter challenges of increased costs and complexity when employing novel materials and structures, with marginal improvements in efficiency. Recently, researchers have proposed a novel optimization approach by focusing on the thermal interface of radiative cooling and thermoelectric generator systems to achieve enhanced thermal concentration, yielding remarkable progress. To elucidate the specific impact of altering thermal interface conditions on system performance, we employed a controlled variable approach and conducted simulations using COMSOL Multiphysics software, investigating various thermal boundary conditions, including dimensions and thermal conductivity, on the temperature differential and output voltage of the system. Following optimization of the thermal interface conditions, the radiative cooling-thermoelectric generator system (RC-TE) generated an output voltage of 0.36082V. This represents a 2.23-fold increase in output voltage compared to the unoptimized RC-TE system, which yielded 0.1618V, providing compelling evidence for significant enhancement in system performance.