Resonance-shifting to circumvent reabsorption loss in luminescent solar concentrators

Luminescent solar concentrators (LSCs) provide a simple means to concentrate sunlight without tracking the Sun. These devices absorb and then re-emit light at a lower frequency into the confined modes of a transparent slab, where it is guided towards photovoltaic cells attached to the slab edges. In the thermodynamic limit, a concentration ratio exceeding the equivalent of 100 suns is possible, but, in actual LSCs, optical propagation loss (due mostly to reabsorption) limits the concentration ratio to ∼10. Here, we introduce a general, all-optical means to overcome this problem by 'resonance-shifting', in which sharply directed emission from a bilayer cavity into the glass substrate returns to interact with the cavity off-resonance at each subsequent bounce, significantly reducing reabsorption loss en route to the edges. Using this strategy, we demonstrate near-lossless propagation for several different chromophores, which ultimately enables a more than twofold increase in concentration ratio over that of the corresponding conventional LSC.