On the combination of fluorescence and phosphorescence in light-emitting materials for a longer energy-saving effect within the built environment

In recent years, the building sector has become one of the major contributors to energy consumption, exacerbating urgent problems like global warming and the urban heat island (UHI) phenomenon. Luminescent materials have recently gained attention as an avant-garde option for energy-saving purposes, thanks to their capability to emit light upon being exposed to solar or artificial radiation. Indeed, the phosphorescent emission has proved not only to guarantee a renewable luminous gain but also to amplify the material’s rejection of the incident solar radiation, resulting in cooler urban skins. Nevertheless, the need to increase the luminescence performances, especially in terms of durability, has emerged as fundamental issue for the effective implementation of luminescent materials in the built environment. The present work aims at investigating for the first time the emission persistency of combined fluorescent (F) and phosphorescent (P) materials. In particular, F and P pigments are mixed in different concentrations to enhance the overall luminescence brightness and duration. Their characterization is preliminary carried out at a laboratory scale, using monochromatic excitation. Results show how the interaction between phosphorescence and fluorescence is actually possible, toward advanced responsive materials for the built environments.