Luminescent solar concentrators: boosted optical efficiency by polymer dielectric mirrors

• Published in: Materials chemistry frontiers 2019-03, Vol.3 (3), p.429-436
• Main Authors: Iasilli, G, Francischello, R, Lova, P, Silvano, S, Surace, A, Pesce, G, Alloisio, M, Patrini, M, Shimizu, M, Comoretto, D, Pucci, A
• Format: Article
• Language: English
• Subjects: Bragg reflectors; Cellulose acetate; Concentrators; Diffusers; Efficiency; Nanocomposites; Optical properties; Photonic band gaps; Photonics; Refractivity; Stacks; Thin films
• ISSN: 2052-1537; 2052-1537
• DOI: 10.1039/c8qm00595h

We report on the optical efficiency enhancement of luminescent solar concentrators based on a push-pull fluorophore realized using high dielectric contrast polymer distributed Bragg reflectors as back mirrors. The Bragg stacks are obtained by alternating layers of cellulose acetate and thin films of a new stable and solution processable hydrated titania-poly(vinyl alcohol) nanocomposite (HyTiPVA) with a refractive index greater than 1.9 over a broad spectral range. The results obtained with these systems are compared with enhancements provided by standard Bragg reflectors made of commercial polymers. We demonstrate that the application of the Bragg stacks with photonic band-gap tuned to the low energy side of the dye emission spectrum induces a 10% enhancement of optical efficiency. This enhancement is the result of a photon recycling mechanism and is retained even in a scaled-up device where the Bragg mirrors are used in a mosaic configuration. High dielectric contrast polymer dielectric mirrors are used to recycle non-absorbed photons in organic luminescent solar concentrators. A 10% increase in the concentrator optical efficiency is found and retained upon doubling its size paving the way to lightweight and cheap building integrated photovoltaic systems.