Luminescent Solar Concentrators: Effect of Dye Structure on Fluorescence Properties and Device Performances

Luminescent Solar Concentrators (LSC) are a class of optical devices able to harvest, downshift and concentrate sunlight thanks to the presence of emitting materials embedded in a polymer matrix. Due to the low-priced materials and their innovative aesthetic properties, LSCs find an easy integration in architectural systems, such as roofs, windows, canopies, and greenhouse, matching the current push toward more sustainable and energy efficient structures.[1] The choice of the proper organic fluorophore is fundamental to achieving good performance. It needs to meet several criteria: broad absorption range, large Stokes shift, high fluorescence quantum yield, precise matching between dye emission wavelength and PV absorption band, good optical efficiency, and good dispersion in the host materials.[2] In this work, we present the design, synthesis, characterization and application in LSC of a series of orange/red organic emitters featuring a benzo[1,2-b:4,5-b?]dithiophene 1,1,5,5-tetraoxide central core as an acceptor (A) unit. The latter was connected to different donor (D) and acceptor (A') moieties by means of Pd-catalyzed direct arylation reactions, yielding compounds with either symmetric (D-A-D) or nonsymmetric (D-A-A') structures. The LSCs built with such compounds presented interesting optical and photovoltaic properties, which are greatly influenced by the nature of the substituents. A precise design of the fluorescent emitter brought performances close to the state-of-the-art, coupled with sufficient stability in accelerated aging tests.