9H-carbazole and indolo[3,2-b]indole-based fluorophores for potential application in luminescent solar concentrators

In the present study, four new organic fluorophores, consisting of a central 9H-carbazole (CBZ) or indolo[3,2-b]indole (IDID) moiety, functionalized with (S)-3,7-dimethyl-1-octyl branched chains and connected to lateral 2-thienylethynyl or 2-thiophenylpropynone units, were synthesized by means of Pd-catalyzed cross-coupling reactions and investigated for potential application in luminescent solar concentrator (LSC) systems. The photophysical properties of four final dyes were first evaluated in solution of four solvents with different polarity (toluene, chloroform, acetone, acetonitrile). For the IDID-based compound 4, which proved to be the best candidate, the photophysical properties in thin films with PMMA matrix at different concentrations (0.4–2.0 wt%) were also investigated. Finally, their efficiency parameters as LSC systems connected to a photovoltaic (PV) cell were evaluated, obtaining a maximum device efficiency (ηdev) of 0.46 ± 0.02 % at 1.2 wt%: these are very promising PV performances for a N-heteroarene-based dye, coupled with a sufficient stability in accelerated aging tests.