Efficiency boosting of silicon solar cell via radiative cooling

Global photovoltaic efficiency faces fundamental thermodynamic constraints: commercial silicon solar cells lose over 4% relative efficiency per 10°C temperature rise—a penalty translating to terawatt-hour annual losses at gigawatt scale1–7, while conventional cooling methods exacerbate water8–16 and energy17–19 footprints. Current radiative cooling solutions20–24, limited by near-saturated infrared emissivity (>0.8)25 on solar cell’s top surfaces, achieve marginal sub-1% efficiency gains. We break this paradigm with a Bottom-surface Enhanced Radiative Cooling (BERC) method that exploits previously untapped thermodynamic potential: redirecting bottom-surface thermal emissions skyward via an inverse-designed, fabrication-tolerant freeform reflector. By utilizing Bayesian-optimized NURBS surface curvature, our design achieves 84% blackbody-equivalent radiation transfer within just 0.84× source footprint while tolerating large surface errors (±2% performance loss at 2 mm deviations) than nanophotonic alternatives. Field validation under 800 W/m² irradiance demonstrates >13°C temperature reduction versus commercial solar cells, translating to 6.33% efficiency gain. This passive cooling further enables potential lifetime doubling per Arrhenius aging kinetics. BERC establishes a new photonic-thermodynamic framework for sustainable energy harvesting by minimizing waste heat and enhancing watts.