Targeted design leads to tunable photoluminescence from perylene dicarboxdiimide-poly(oxyalkylene)/siloxane hybrids for luminescent solar concentrators

A series of organic-inorganic hybrid materials in which a perylene carboxdiimide-bridged triethoxysilane (PDI-Sil) is covalently grafted to the siliceous domains of poly(oxyalkylene)/siloxane hybrids from the ureasil family has been synthesised (PDI-Sil-ureasils), with the aim of tailoring the optical properties towards their future application in luminescent solar concentrators (LSCs). Steady-state and time-resolved photoluminescence studies revealed that the ureasil host is able to isolate PDI-Sil, which inhibits the formation of aggregates. The ureasil also functions as an active host, with its intrinsic photoluminescence contributing to the optical properties of the hybrid material. Through strategic variation of the branching and molecular weight of the poly(oxyalkylene) backbone, it was shown that the efficiency of energy transfer from the ureasil host to the PDI-Sil can be modulated, which tunes the emission colour from pink to orange. The chain length, rather than the number of branches, on the poly(oxyalkylene) backbone was shown to influence the photoluminescence most significantly. Since ureasils demonstrate waveguiding properties, the results indicate that covalent grafting of a fluorophore directly to a waveguide host may provide an attractive route to more efficient LSCs.