TiO₂ particle agglomeration impacts on radiative cooling films with a thickness of 50 μm

The random micro-particle-embedded thin film is an inexpensive and scalable structure for radiative cooling (RC). However, current investigations on evaluating the performance of such films assume that the embedded particles are perfectly separated from each other. The particle agglomeration effects on the spectral characteristics of the film are dismissed. In this work, by comparing the spectral reflectivity and emissivity of a film composed of perfectly separated TiO₂ particles, three-particle aggregations, five-particle aggregations, and ten-particle aggregations, we studied the particle agglomeration impacts on the performance of a disordered radiative cooling film with a thickness of 50 μm. The results show that the agglomeration suppresses the solar reflectivity of the particle-embedded film and harms the temperature drop and cooling power in RC applications. Therefore, particle agglomeration is intended to be industriously eliminated in the preparation of a random particle-embedded thin film for radiative cooling. The results in this paper provide a further explanation of the difference between the theoretical calculations and experimental measurements of the cooling performance of a particle-embedded RC film.