High transmittance, fast response, and high contrast ratio smart window with lateral driving electrophoretic display

Smart windows can dynamically control the optical transmittance of natural light and efficiently reduce the energy consumption of buildings. Currently, the practical application of smart windows is limited by high power consumption, low transmittance, and complicated preparation process. Developing smart windows with fast response and high transmittance is challenging. Herein, we fabricated a smart window based on electrophoretic display (EPD) technology, which can switch between white and transparent states by changing the stacking states of the electrophoretic particles on electrodes. To further increase the transmittance of the smart window, the polyvinyl alcohol (PVA) hydrophilic layer was spin-coated on the electrode to reduce the adhesion of particles. Compared with other EPD smart window technologies, our device exhibits the fastest response time of up to 375 ms at 30 V, high transmittance of up to 78% at 632 nm, and a high contrast ratio of up to 89. In addition, to reduce the particle’s lateral diffusion and improve our device's stability, the microcup array was aligned on the interdigital electrode. The particles can be driven and stacked onto the side walls of the microcup to achieve a transparent state. This work demonstrated that the EPD device would provide a promising future for practical smart windows with high transmittance and fast response time.