Thin-Film Luminescent Solar Concentrators with good properties by using D-A-D Organic Fluorophores

Luminescent solar concentrators (LSCs) is a technology developed since the 1970s[1] with the aim of obtaining large-area, semi-transparent and cheap photovoltaic devices capable of concentrating solar radiation on small solar cells at their margins. Specifically, they consist of a panel of a standard plastic material (e. g., poly(methyl methacrylate), PMMA) in which a fluorescent compound, able of absorbing direct and indirect sunlight radiation and emitting it at a different, usually longer wavelength, is dispersed. Commonly used fluorescent compounds can be quantum dots, perovskites, rare-earth complexes and organic molecules[2]. Thanks to the different refractive indexes of air and the plastic material, the emitted radiation is mainly concentrated via total internal reflection at the edge of the panel, where the solar cells are usually placed, making the device less dependent on light orientation. This, together with the aesthetic characteristics (colour and shape tunability), allows their use in building-integrated photovoltaics (BIPVs)[3]. In order to obtain high-performance LSC devices, a careful study of the materials used for their assembly must be performed, both concerning the selection of the fluorophore and the plastic material in which it is dispersed[2]. We recently synthetized and investigated the properties of a series of organic fluorophores with donor-acceptor-donor (D-A-D) structure, characterized by a benzo[1,2-d:4,5-d']bisthiazole[4] and quinoxaline[5] as acceptor core. The optical properties of the molecules were investigated in solution as well as after dispersion in PMMA and its copolymer with more apolar cyclohexyl methacrylate repeating units. The variation of the absorption and emission maxima, the fluorescence quantum yields and the optical efficiency of the corresponding LSC devices were eventually determined. Due to the very good fluorophores compatibility with the polymeric matrices, LSCs with optical features superior to the state-of-the-art were obtained[4,5].