Optimizing Perception and Efficiency: Lead-Free Perovskite Nanocrystals for Enhanced Passive Daytime Radiative Cooling in Urban Environments

To address the challenge of passive daytime radiative cooling (PRDC) applications in the built environment, silver or aluminum solar-reflective substrates are commonly used. However, their limited aesthetics hinder real-scale implementation in the large-scale urban context. Recent efforts to introduce colored radiative coolers have been facing issues, as the effective absorption of visible light contributes to surface heating, thus compromising the cooling performance. In this context, this work explores the outstanding properties of lead-free perovskite nanocrystals (NCs) as cost-effective layers to provide color to the PDRC structures while improving the rejection of shortwave radiation through photoluminescence mechanism. By combining different NCs emitting in blue, green and red regions, color can be tailored to this aim, offering a promising strategy for the optimal integration of PDRCs into the existing urban fabric. In addition, the inclusion in polymer matrices produced colored thin films with good stability and efficient response in the atmospheric windows wavelengths (ε(8–13 µm) = 0.90). Finally, the integration of lead-free perovskite films in PDRC structures has been examined, aiming to definitively harness the crucial potential of radiative cooling in enhancing building energy performance and counteracting UHI.