Investigation of polyesters as daytime radiative cooling materials

We discovered that polyesters, particularly polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), are potential candidates for daytime radiative cooling (RC). A significant temperature drop was observed in both PET and PEN films when they were exposed to liquid nitrogen. In addition, their RC efficiency was compatible with previously reported RC materials such as polydimethylsiloxane and soda-lime glass. Polyesters have advantages over other RC materials in terms of chemical stability, moldability, and impact resistance. In particular, PET can be utilized for daytime RC of solar cells due to its transparency in the visible region.