Highly emissive fluorescent silica-based core/shell nanoparticles for efficient and stable luminescent solar concentrators

Luminescent solar concentrators (LSCs) represent a viable spectral conversion technology to maximize sunlight harvesting while promising to reduce the current gap for integration of solar cells into the built environment. In this work, novel highly emissive and photostable core-shell nanostructured luminescent species were synthesized and used in LSC devices. Such systems were obtained by entrapping Lumogen F Red 305 in silica-based shells by means of the sol-gel process using a combination of hydrophilic (tetraethyl orthosilicate) and hydrophobic (phenyltriethoxysilane) silica precursors. By tuning their relative proportions during the synthetic process, fine control over the characteristic dimensions and morphology of the obtained dye-doped core-shell nanoparticles could be achieved, leading to a maximum concentration of non-covalently entrapped fluorescent dye of ~ 1 wt%. Optical characterization showed that the newly synthetized nanoparticles displayed markedly improved photoluminescence quantum yield in solid state (~ 95%) with respect to the non-encapsulated dye (~ 2%), as a result of an effective suppression of dye aggregation and fluorescence quenching phenomena. In addition, their excellent photostability under harsh UV light exposure was demonstrated, resulting from the protective action of the encapsulating hybrid silica-based shell, which can effectively limit photobleaching of the luminescent core. Their incorporation in thin-film LSCs led to a maximum internal photon efficiency as high as ~ 29%, thus providing evidence of their suitability as highly performing luminescent species with superior optical response and excellent photostability. Also, a maximum external photon efficiency as high as 2.12% was achieved. This work provides the first demonstration of silica-based encapsulation of Lumogen F Red 305 and of the application of silica-based core-shell nanoparticles in LSCs, thus paving the path to the development of a new class of highly efficient and stable nanostructured luminophores for the photovoltaic field.