Five extended π‐conjugated systems with electron donor (D) and acceptor (A) moieties have been synthesized. Their basic D‐A‐D structural motif is a benzothiadiazole unit symmetrically equipped with two thiophene rings (S2T). Its variants include 1) the same molecular framework in which sulfur is replaced by selenium (Se2T), also with four thiophene units (Se4T) and 2) a D’‐D‐A‐D system having a N‐carbazole donor moiety at one end (CS2T) and a D’‐D‐A‐D‐A’ array with a further acceptor carbonyl unit at the other extremity (CS2TCHO). The goal is taking advantage of the intense luminescence and large Stokes shifts of the five molecules for use in luminescent solar concentrators (LSCs). All of them exhibit intense absorption spectra in the UV/Vis region down to 630 nm, which are fully rationalized by DFT. Emission properties have been studied in CH2Cl2 (298 and 77 K) as well as in PMMA and PDMS matrices, measuring photoluminescence quantum yields (up to 98 %) and other key optical parameters. The dye–PMMA systems show performances comparable to the present state‐of‐the‐art, in terms of optical and external quantum efficiencies (OQE=47.6 % and EQE=31.3 %, respectively) and flux gain (F=10.3), with geometric gain close to 90. LSC devices have been fabricated and tested in which the five emitters are embedded in PDMS and their wave‐guided VIS luminescence feeds crystalline silicon solar cells.
Luminescent solar concentrators (LSCs) are an attractive architectural solution as building‐integrated photovoltaics for renewable electricity production in urban settings, on the way to self‐sufficient housing. When embedded in polymer matrices, bright benzoheterodiazole dyes with large Stokes shifts produce LSCs with state‐of‐the‐art optical and external quantum efficiency. Cover design by Gaia Barbieri. More information can be found in the Full Paper by N. Armaroli, K. Yoosaf, A. Barbieri et al. on page 11013).
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