Thienopyrazine-Based Fluorophores for Application in Luminescent Solar Concentrators (LSCs)

The development of new technologies for converting sunlight into other forms of energy, such as electricity, is widely regarded as a promising approach to ease the World's dependence on energy production by fossil fuels. In this context, luminescent solar concentrators (LSCs), coupled with traditional silicon photovoltaics, appears as a promising solution. Organic conjugated fluorophores have found broad application as emitters in LSCs, but the development of systems with high absorption efficiency, emissions in the deep-red and NIR regions, and large Stokes shift values is still a challenging goal. Recently, thienopirazine core has been shown as an attractive and unique acceptor building block to be employed to prepare donor-acceptor (D-A) type chromophores. In this study, we report the synthesis and the spectroscopic characterization of a new small family of D-A-D dyes (1a, 1b and 1c)3. In particular, we focused on the structure-property relationships and explored their potential employment as NIR-emitting fluorophores for LSC application. Compounds 1a-c were prepared using an efficient and general procedure, leading to good overall yields. For all the dyes, spectroscopic and solvent-dependent photoluminescence studies were carried out. In all cases, emissions extending to the IR and NIR regions and large Stokes shifts were found, highlighting these molecules as promising emitters for application in LSCs. Finally, compound 1c was dispersed in a PMMA matrix to prepare the corresponding LSC devices, whose optical efficiencies were measured and compared with a classical reference dye, BASF Lumogen Red 305 (LR 305).