Unlocking the cooling power of photoluminescent materials: Experimental validation of a correction procedure for effective solar reflectance measurement

Photoluminescent (PL) materials have recently emerged as promising heat-rejecting solutions for mitigating Urban Heat Islands (UHIs), although quantifying their contribution to heat dissipation remains challenging. This study experimentally validates an innovative procedure based on optical and photometric measurements to determine the effective solar reflectance (ESR) of PL materials. By isolating the re-emission component from the overall solar response, the cooling potential of five tiles with increasing concentrations of yellow-emitting pigments is quantitatively assessed for the first time in terms of reduced solar absorption and enhanced thermal performance. The accuracy of the analytical correction in reproducing experimental reflectance data is confirmed through statistical validation (RMSE 3% and R 0.96). Results reveal that higher pigment concentrations improve persistent PL performance, enhancing both luminous intensity and afterglow duration, but can also induce increased surface roughness. These morphological changes promote self-absorption phenomena and quench the emission under direct solar irradiation, ultimately reducing the net PL contribution to cooling. By enabling the experimental quantification of reflected and re-emitted components of solar energy, this validated procedure provides a critical tool for assessing the performance of a broad range of PL materials in mitigating the UHI effect.