Enhanced Photon Collection in Luminescent Solar Concentrators with Distributed Bragg Reflectors

Escape cone loss is one of the primary limiting factors for efficient photon collection in large-area luminescent solar concentrators (LSCs). The Stokes shift of the luminophore, however, opens up an opportunity to recycle the escaped luminescence at the LSC front surface by utilizing a photonic band-stop filter that reflects photons in the luminophore's emission range while transmitting those in its absorption range. In this study, we examine the functional attributes of such photonic filter designs, ones realized here in the form of a distributed Bragg reflector (DBR) fabricated by spin-coating alternating layers of SiO₂ and SnO₂ nanoparticle suspensions onto a supportive glass substrate. The central wavelength and the width of the photonic stopband were programmatically tuned by changing the layer thickness and the refractive index contrast between the two dielectric materials. We explore the design sensitivities for a DBR with an optimized stopband frequency that can effectively act as a top angle-restricting optical element for a microcell-based LSC device, affording further capacities to boost the current output of a coupled photovoltaic cell. Detailed studies of the optical interactions between the photonic filter and the LSC using both experimental and computational approaches establish the requirements for optimum photon collection efficiencies.