Analysis of fluorescent additives for enhancing solar reflectivity in TiO2 based coatings

TiO${}_2$-based coatings are widely used for passive daytime radiative cooling. However, intrinsic UV absorption by TiO${}_2$ particles limits their total solar reflectivity to approximately 88%–90%, thereby reducing their cooling performance. To address this limitation, fluorescent particles with excitation spectra overlapping the UV absorption band of TiO${}_2$ have been investigated in prior studies as a means to enhance solar reflectivity. In this work, we use a fluorescent-based Monte Carlo simulation to study the impact of embedding BaMgAl₁₀O₁₇:Eu${}^{2+}$ (BAM) fluorescent particles on the radiative properties of TiO${}_2$-based coatings. Simulation results show that simply mixing fluorescent particles with TiO${}_2$ yields only a modest increase ($\approx$1 percentage point) in solar reflectivity. To overcome this, we propose a modified configuration in which a separate fluorescent layer is applied on top of the TiO${}_2$ coating. This double-layer design leads to a more significant enhancement, increasing solar reflectivity by 2.1 percentage points.