Tuning Radiative Properties of Multiscale Porous Transparent Silica Aerogels for Efficient Solar Interfacial Evaporation

ABSTRACT High‐efficiency multistage solar interfacial evaporation requires covers that maximize solar spectrum transmission to the absorber while limiting thermal losses. Here, we establish a coupled numerical and experimental framework to tune the optical properties of transparent silica aerogels.We identify wavelengths < 500 nm as a critical, morphology‐tunable scattering regime that also coincides with the AM 1.5G peak. Design maps suggest an optimal design in which a mean particle radius < 4 nm and a bulk density < 200 kg m −3 deliver total transmittance > 95% with haze < 5%. Further promotion in forward scattering can boost the transmittance even when haze is relatively high. Experimentally, guided by the multiscale model, we tuned the sol‐gel process to reduce the silica aerogel mean scattering center radius from 4.9 to 3.1 nm, yielding a 5 mm‐thick sample with a solar‐weighted transmittance of 95.2%. Integrated as a greenhouse‐selective cover in a 10‐stage solar evaporation device, the optimized silica aerogel boosts the water production rate by 19.3%, from 5.22 to 6.23 kg m −2 h −1 , demonstrating that morphology tuning translates into system‐level performance gains. These results provide actionable design rules and a validated predictive modeling framework for low‐haze and high‐transparency aerogel covers that enable efficient solar evaporation.