Luminescent Perovskite nanocrystals: synthesis, characterization and prospects in Luminescent Solar Concentrators

Metal Halide Perovskites are currently under the spotlight as some of the most promising materials of the 21st century, due to the ease with which they can be synthesized as well as their tunable optical properties. Doping CsPbCl3 with lanthanides is a promising way to realize UV-to-NIR down-conversion, which paves the way for many applications, from optoelectronics to photovoltaics. Lanthanides ions occupy some of the lead reticular positions: these punctual defects and lead vacancies modify the band edge structure of the hosting lattice, introducing electronic states within the band gap. The peculiarity of Yb3+ doping is the effect termed quantum cutting, in which photons absorbed at the perovskite bandgap are re-emitted through the f-f transitions of Yb3+, leading to the emission of two NIR photons per absorbed UV photon. Driven by punctual defects, this process can exhibit outstanding luminescence yields in the near IR. As the NIR window is the spectral region in which silicon-based photovoltaic modules show high efficiency, embedding Yb3+: CsPbCl3 NCs in a PMMA matrix, allows the realization of fully transparent solar concentrators (LSCs). In this thesis, CsPbX3 (X=Br, Br/Cl, Cl) and Yb3+: CsPbCl3 nanocrystals, synthesized via hot injection, were studied as colloidal dispersions and characterized using optical spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The effect of the magnetic field, in emission and in absorption, was detailed by means of Magnetic Circular Dichroism (MCD), and Magnetic Circularly Polarized Luminescence (MCPL). Moreover, Luminescent Solar Concentrators, in the form of thin PMMA films doped by Yb3+: CsPbCl3 and CsPbBr3 nanocrystals, were prepared and characterized in terms of their optical efficiencies.