Francesco Meinardi1

1, Department of Materials Science, University of Milano-Bicocca, Bicocca, , Italy

Luminescent solar concentrators (LSCs) could facilitate the green architecture revolution by enabling the realization of semi-transparent photovoltaic (PV) systems, which could potentially convert the façades of urban buildings into distributed electrical power generators. LSCs were first proposed in 1976 as cost-effective alternatives to silicon solar cells. However, only after the recent breakthroughs in the realization of new classes of colloidal semiconductor nanocrystals, which combine suppressed reabsorption with broadband spectral coverage, the performances of the LSCs have been boosted to such a degree that they become the most promising technology for the next generation of PV glazing units. The LSC technology is now set on a clear path to become a PV technology that can be ‘invisibly’ integrated into the built environment without detrimental effects to the aesthetics of the building or the quality of life of the inhabitants in the form of colorless and electrodeless solar windows or as other semi-transparent architectural elements. Nevertheless, this final integration step, and in particular the optimization of the power efficiency for devices on the meter scale, will require scientists and engineers to face new emerging challenges.
This talk will review the successful strategies that have allowed this historical change of pace, examining and comparing the different types of developed nanomaterials, and discuss the issues that remain to be investigated for further progress. On the materials side, the realization of high-quality optical waveguides will be the most demanding task. It will require a perfect dispersion of the nanocrystals inside the waveguide matrix to avoid detrimental light-scattering losses and, probably, also the adaptation to LSCs of highly transparent polymers or glass variants currently used in photonics and telecommunications will be necessary to produce very large LSCs. Finally, the optical-to-electrical conversion by the PV cells at the LSC edges will have to be suitably designed and optimized. This last step in the luminescent solar concentration process has not yet been fully investigated because of the challenges in the realization of highly performing optical waveguides. Together with the role of the waveguide absorption, this will soon be at the forefront of research into LSCs for real-world applications.