Replacing Lumogen Red from High Optical Efficiency Luminescent Solar Concentrators: the Example of a Red-Emitting Silafluorene Dye

Luminescent solar concentrators (LSCs) have been widely studied as a viable alternative to decrease the price of photovoltaic energy. We report on the optical efficiency (ηopt) of LSCs based on poly(methylmethacrylate) (PMMA) thin-films doped with a red-emitting 2-amino-7-acceptor-9-silafluorene, where the amino group is –N(CH3)2 and the acceptor is –CH=C(CN)2. The photophysical characteristics of the dye in different solvents and in the PMMA matrix are first analysed. Then, in order to assess the performances as LSC, an optically pure glass was coated with the dye-doped PMMA films at different dye weight percent. Photocurrent measurements were accomplished. Furthermore, ηopt was evaluated from the concentration factor C, which is the ratio between the short circuit jcurrent measured in the case of the cell over the LSC edge (ILSC) and short circuit current of the bare cell put perpendicular to the light source (ISC). Overall, the results obtained are very encouraging as the silafluorene dye analysed turned out to be stable upon irradiation, highly emissive and well dispersed in the polymer matrix. Moreover, the concentration factor at 1.5 wt.% dye is 9.4%, i.e. at the top level respect to the current state-of-art of similar devices based on perylene-based fluorophores such as Lumogen Red.