Enhanced Coloration/Bleaching Photochromic Performance of WO3 Based on PVP/PU Composite Matrix

Photochromic WO3 based smart window owns special advantages such as simple construction, automatic modulation and great solar regulation, so it can be used to reduce the energy consumption of building industry. In this paper, we studied the relationship between WO3 and the composite matrix composed of different proportions of polyurethane (PU) and polyvinyl pyrrolidone (PVP). Fourier-transform infrared spectra and Raman spectra has demonstrated a strong interaction between WO3 and PVP, leading to a high regulation efficiency of WO3 in PVP. While in pure PU, the nonbonding between WO3 and PU leads to a faster bleaching speed. By tuning the proportion of PU and PVP in the matrix, WO3-based hybrid photochromic foil was obtained with rapid coloration (< 5 min), fast bleaching behavior (< 3 hours at room temperature or < 1 hour at 60 degrees C), and exhibited good cycling stability. This study proposes a simple strategy for widespread application of WO3-based photochromic smart window.