Effect of VO₂ particle aggregation on the performance of thermochromic smart window films for building

The energy efficiency of smart windows plays a crucial role in reducing building energy consumption, and VO₂ particle-based films are widely studied due to their potential for large-scale application. However, current research often assumes that VO₂ particles are completely dispersed, overlooking the impact of aggregation on optical performance. This study systematically investigates the effects of different sizes, aggregation types, and aggregation degrees of VO₂ particles on the optical performance of smart windows using the FDTD method. The results show that particle aggregation leads to an increase in scattering efficiency and causes a redshift and broadening of the absorption peak. As the number of aggregated particles increases, both τ_lum and Δτ_sol decrease significantly. Additionally, larger particle sizes further exacerbate this negative impact. When the particle size increases from 30 nm to 100 nm, the decrease in τ_lum caused by aggregation increases from 10.85 % to 20.97 %, and the reduction in Δτ_sol rises from 8.18 % to 67.79 %. Further analysis shows that higher degrees of aggregation result in more pronounced declines in optical performance. Therefore, when preparing VO₂-based films for smart windows, measures should be taken to minimize particle aggregation, while appropriately reducing particle size and adjusting inter-particle spacing to effectively mitigate the negative effects of aggregation on optical performance.