In the last decade, lead-halide perovskites have gathered significant attention due to their fascinating optoelectronic properties which make them suitable for a plethora of applications (e.g. solar cells, light-emitting diodes, scintillators, thermoelectric devices, lasers). The versatility of these materials results from the possibility to tune their properties by directly manipulating their chemical composition and structure. To make full use of this tunability we need to be able to understand the relationship between structure and properties. Due to the strong connection between structural and optoelectronic properties, external pressure and, more in general, strain, can be used to manipulate the optical properties of these materials targeting specific device applications. Chapter 1 starts with an introduction to lead-halide perovskites and to their peculiar electronic structure highlighting how strain can affect the optical properties of such materials. Chapter 2 investigate two different fabrication methods of perovskite thin films. The fabrication results in different crystal growth. EBSD and spatially-resolved photoluminescence are used to correlate structural and optical properties of such films. Chapter 3 presents an investigation on the hot-carrier cooling process. We investigate how manipulating the lattice properties by applying external pressure affects the rate at which the hot electrons cool to the lattice temperature. Pressure has also an effect on the phase stability of mixed-halide perovskites, being an effective tool to manipulate the thermodynamics and kinetics of phase segregation as reported in Chapter 4. Finally, in Chapter 5 the structure-properties relationship in 2D perovskites is investigated.