Functional dye-doped liquid crystal smart windows: From sunlight manipulation to sunlight utilization

Liquid crystals are crucial to dynamic control over light transmission to fulfill various demands in energy saving, privacy protection, and information display, emerging as a promising choice for smart windows. Nevertheless, owing to the limitation of mesogenic materials, the functions of many liquid crystal smart windows cannot meet the needs of practical applications, and their application scenarios are also suppressed. Particularly, conventional liquid crystal windows focus on sunlight manipulation while neglecting sunlight utilization. To address the demands of multifunctionality and practicality, the combination of mesogenic materials and functional dyes provides a judicious strategy to ameliorate functions for smart windows. In this review, the recent developments in functional dye-doped LC smart windows are summarized and the roles of the dyes in sunlight manipulation and sunlight utilization are highlighted. The general configuration and working principles for liquid crystal smart windows are elucidated. The working principle and sunlight dimming/utilization effects of the LC windows doped dichroic dyes, photoactive dyes, and photothermal dyes are outlined. Finally, the development trends and prospects of smart windows from dye-doped LC materials are also pointed out.