Solar energy and radiative cooling (RC)-driven thermoelectric generator (TEG) technology, which harnesses the extraterrestrial heat and cold sources from the sun and deep universe, is attracting increasing attention. However, existing studies on solar TEG (STEG) and RC TEG (RCTEG) only focus on either solar spectrum or infrared spectrum. To investigate the TEG performance considering full spectrum’s influence, a thermal-electrical coupled model based on thermal resistance theory is developed. Results indicate the TEG with ideal selective absorber (ISA) provides the best power generation performance, with a power generation of around 2.06 W/m² and a temperature difference of about 3.18 K. The maximum power generation is 2.89 and 2.87 W/m² for the ISA and ideal broadband absorber (IBA) systems when the bottom cooling temperature is 275 K, respectively. For every 100 W/m² increase in solar irradiance, there is a temperature difference increment of about 0.31 K. The IBA and ideal selective absorber and emitter (ISAE) systems are capable of generating electricity continuously, ensuring a 24-hour power supply. Moreover, the radiative cooling capacity provided by the ISAE system is greater than that of the RCTEG system. The proposed STEG system has promising application potential for power generation in view of its carbon footprint features.