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Smart solar windows with tunable light trapping enabled by polymer dispersed liquid crystals (Conference Presentation)

Windows provide an attractive platform for building integrated photovoltaics due to the presence of an existing glass substrate and their widespread deployment. A challenge in implementing integrated photovoltaics within windows are the competing design criteria between window transparency and solar cell efficiency. A common approach to address this conflict is to use a solar cell device with partially transparency in the visible range and strong light absorption in the UV and/or IR ranges. Recent research has also attempted to circumvent this trade-off using switchable materials that can transform from opaque and efficient to transparent but with poor photovoltaic performance. Here, we present a new alternative switchable device approach that couples a semiconductor solar absorber to a Polymer Dispersed Liquid Crystal (PDLC) cell. By applying an electric field these PDLC devices can be dynamically tuned from opaque, reflective and light diffusing in the off state to clear and transparent in the on state. By enabling light-trapping to greatly enhance solar cell efficiency, this off-state scattering makes PDLCs a particularly attractive option for the creation of solar windows. As an added benefit, the system provides control over haze for privacy and window reflectivity for reducing the lighting and heating costs. Enabled by the very low power requirements for maintaining the window’s transparent on-state, we also demonstrate potential for self-powering this switchable solar window.