Tris-Ethynylphenyl-amine Fluorophores: Synthesis, Characterisation and Test of Performances in Luminescent Solar Concentrators

Two fluorescent dyes (CT-tEPhA=3,3′,3′′-(nitrilotris(benzene-4,1-diyl))tris(1-(thiophen-2-yl)prop-2-yn-1-one and T-tEPhA=tris(4-(thiophen-2-ylethynyl)phenyl)amine) have been synthesised and characterised in different solvents and in a poly(methyl methacrylate) (PMMA) matrix. In both cases, relatively high Stokes shifts (SS) and quantum yields (QY) have been displayed. Notably, CT-tEPhA based on a mild electron-attracting carbonyl group coupled with the electron-donating amino-centre, shows superior light emitting properties (higher SS, red-shifted emission, QY > 40%) suggesting application in light harvesting systems. Photocurrent measurements of CT-tEPhA/PMMA films yield a maximum optical efficiency of 6.32% that is greater than that of fluorophores with same emission window and comparable to that of red-emitting ones. This efficiency might be improved by extending the push-pull character of CT-tEPhA to cover the maximum efficiency of the Si-based PV cell. Nevertheless, these results clearly support the use of push-pull fluorophores based on the tris(4-ethynylphenyl)amine core in solar collectors.