Lanthanide doped ultrafine hybrid nanostructures: multicolour luminescence, upconversion based energy transfer and luminescent solar collector applications.

We herein demonstrate novel inorganic-organic hybrid nanoparticles (HNPs) composed of inorganic NPs, NaYErYbF, and an organic β-diketonate complex, Eu(TTA)Phen, for energy harvesting applications. Both the systems maintain their core integrity and remain entangled through weak interacting forces. HNPs incorporate the characteristic optical behaviour of both the systems i.e. they give an intense red emission under UV excitation, due to Eu in organic complexes, and efficient green upconversion emission of Er in inorganic NPs for NIR (980 nm) excitation. However, (i) an energy transfer from Er (inorganic NPs) to Eu (organic complex) under NIR excitation, and (ii) an increase in the decay time of D → F transition of Eu for HNPs as compared to the Eu(TTA)Phen complex, under different excitation wavelengths, are added optical characteristics which point to an important role of the interface between both the systems. Herein, the ultra-small size (6-9 nm) and spherical shape of the inorganic NPs offer a large surface area, which improves the weak interaction force between both the systems. Furthermore, the HNPs dispersed in the PMMA polymer have been successfully utilized for luminescent solar collector (LSC) applications.