"Non-conventional perovskite devices, flexible and with active layers formed by perovskite Quantum Dots "

In this thesis, first, the monolithic integration of a perovskite-based optical waveguide amplifier together with a photodetector on a nanocellulose substrate is shown to demonstrate the feasibility of a stretchable signal manipulation and receptor system fabricated on a biodegradable material. An integrated optical amplifier–photodetector is developed in which the photocurrent is exploited that is generated in the organic–inorganic lead halide perovskite under an applied bias. Such photocurrent does not minimally perturb the amplifier operation and is used to monitor the light signal propagating along the waveguide, opening a broad range of applications for example to measure the operation temperature. Then, perovskite quantum dot solar cells (PQDSCs) were systematically investigated with impedance spectroscopy. Despite the evident structural differences with respect to standard perovskite solar cells (PSCs), similar impedance spectra were obtained for PQDSCs, pointing to similar working principles in terms of the active layer. Although there is no consensus about the exact mechanism responsible for low frequency capacitance, the suggested models point to an ion migration origin. Its observation in thin-film and PQDSCs devices implies a similar effect in both. Finally, we synthesized ultra-high stable CsPbI3 QDs by controlling two main parameters: synthesis temperature and the concentration of capping ligands. We achieved the maximum photoluminescence quantum yield (PLQY) of 93% for a synthesis conducted at 185 °C, establishing an efficient surface passivation. Under these optimized synthesis conditions, deep red LEDs with an External Quantum Efficiency (EQE) higher than 6% were achieved. We show that it is possible to produce stable CsPbI3 QDs with high PLQY and red emission beyond the requirement of the Rec. 2020 standards for red color.