Abstract:
Five extended p-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.
