Microstructured Halide Perovskites for Energy Applications

Perovskites are cutting-edge materials that have demonstrated outstanding potential in the field of renewable energy. Their unique chemical-crystalline structure enables the easy substitution of atoms with various elements, allowing for a diverse range of optoelectronic properties that make them especially promising for application in devices. Perovskites can adopt different structural forms, including the polycrystalline one, where the high density of charge traps due to grain boundaries presents a major challenge. These traps not only compromise the device’s efficiency but also accelerate its degradation. To overcome these limitations, single-crystal structures have been developed. These are free of grain boundaries and exhibit trap densities comparable to those of crystalline silicon (approximately 10⁹- 10¹⁰ cm⁻³), along with very high charge carrier diffusion lengths. However, single crystals require growth in extremely thin layers to prevent charge recombination within the bulk, and careful attention to surface quality, where structural defects often form traps. A key strategy to mitigate these issues is passivation, a process that involves applying layers or chemical treatments to reduce surface defects. Passivation minimizes non-radiative recombination, thereby enhancing the optoelectronic performance of the material, which is crucial for improving device stability and efficiency. This thesis presents studies on the synthesis and characterization of various types of perovskites, with a particular focus on their chemical-crystalline compositions and the characterization of their physical properties. Advanced techniques have been developed to control the quality and thickness of materials, ranging from polycrystalline structures to single crystals, ultimately leading to the creation of a heterostructure between two single crystals with precisely controlled thickness. This heterostructure proves especially promising in the field of solar cells, as it enhances the performance of highly efficient yet unstable materials through effective passivation. The work presented offers the possibility of achieving passivation in a single pot process, directly in the form of a single crystal, overcoming the typical limitations of polycrystalline perovskites.