Stimuli‐Responsive Smart Glass with Switchable Unidirectional Light Source for Enhanced Privacy/Indoor Illumination

Abstract Light manipulation is in high demand in science and industry. Smart glasses enable dynamic light control for indoor illumination, privacy protection, automobiles, and displays. However, existing technologies often limit single‐functionality (simultaneous bidirectional transparency or opacity) and strongly inherent user preferences. Here, a novel class of stimuli‐responsive smart glass featuring a switchable unidirectional light source using 2,2‐dimethoxy‐2‐phenylacetophenone (DMPAP)‐doped twisted hybrid polymer network liquid crystals (TH‐PNLCs) with a linear polarizer is developed. These DMPAP‐doped TH‐PNLCs exhibit a blue‐shift in spectra under cross‐polarizer, enhanced twist angle, and increased light amplitude compared with undoped devices. When subjected to external electric stimuli and edge light, the device emits light bi‐directionally with different polarizations. As a proof of concept, placing a transmissive polarizer in front of the homogeneous alignment layer (Surface A) enables light absorption and scattering toward vertical alignment (Surface B), ensuring privacy by blocking visibility from Surface A while keeping Surface B visible. Replacing the transmissive linear polarizer with a reflective one enhances light scattering, boosting intensity from Surface B, making the device ideal for energy‐efficient indoor lighting. Featuring fast switching times and robust endurance, this stimuli‐responsive smart glass offers a pioneering solution for green buildings and automobiles with enhanced privacy and indoor illumination.