Sounds very cool. But why restrict it to windows? Seems any sunlit surface will do.
From the article, it sounds like they need the glass’s internal reflections to transport the photons to the window’s edges - something not doable on a roof shingle, for instance.
"After absorbing solar light shining onto a larger-area face of the slab, LSC fluorophores re-emit photons at a lower energy and these photons are guided by total internal reflection to the device edges where they are collected by photovoltaic cells. "
Those re-emitted photons travel through the glass and are collected at the edges of the glass by photovoltaic cells.
Can't do that with solid brick, or wood.