Comparing a covalently linked BODIPY-pyrene system versus the corresponding physical mixture as chromophores in luminescent solar concentrators

Luminescent solar concentrators (LSCs) appear as an attractive solution to extend the application of photovoltaic panels by installing them "invisibly" in urban architectures. Many researchers are working on boosting the photovoltaic performances of LSCs, and an appealing strategy is to involve a multichromophoric system where Forster resonance energy transfer (FRET) occurs. To investigate the role of the energy donor, which is crucial in FRET processes inside LSCs, we designed a light-harvesting antenna composed of a highly emissive donor, such as pyrene, covalently connected to a BODIPY unit as an energy acceptor. Such an antenna was used as the chromophore to fabricate a LSC and the photovoltaic performance of the device was compared with that of the LSC based on a physical mixture of BODIPY and pyrene not covalently bonded. The results indicate that the LSC based on the antenna system has a lower optical efficiency than the LSC containing the physical mixture. Such a conclusion highlights that designing an antenna system composed of a highly luminescent species as the energy donor (e.g. pyrene, in this case) could not improve the LSC photovoltaic performances compared to the LSC based on the physical mixture of the separated chromophores.