Lead halide perovskites (LHP) are the most promising light harvesting materials that led the surge of perovskite solar cells (PSCs) up to conversion efficiencies well above 20%. [1] Starting from the seminal works employing methyl ammonium lead iodide perovskite (MAPbI₃ or MAPI, with MA = CH₃NH₃), several different LHP compositions have been tested, the best results being so far obtained with a tri-cation and bi-halogenide formulation. [2] Understanding and optimizing the optoelectronic properties of LHPs is of primary importance for advancing this emerging PV technology. Therefore, there is great attention in controlling the fabrication protocols towards specific stoichiometries, but defects are always present [3]: understanding the role of defects in tuning the LHP electronic features is of primary importance for the design of new materials and devices. In this context, we focused on MAPI, the archetype of this class of materials, combining experiment and theoretical calculations. The fabrication of LHP films typically involves solution-based processing, with vapor-based methods being an attractive alternative. Here we used a two-step hybrid approach consisting in thermal evaporation of a PbI₂ template followed by spin-coating of the MAI solution and subsequent thermal annealing. This method provides the advantages of vacuum depositions, while avoiding the issues encountered in the evaporation of the organic precursors. We searched for optimal fabrication conditions and explored possible post-deposition treatments for material optimization. The samples were characterized with XRD, SEM, EDX and Uv-Vis spectroscopy. The material was finally tested as photoactive layer into n-i-p solar cells fabricated onto glass/ITO substrates with SnO₂ and Spiro-OMeTAD as electron and hole transport layers, respectively, and Au as back electrode. From the computational perspective, the effects of punctual defects like Pb/MA/I/MAI vacancies on the electronic structure of the MAPI tetragonal phase (space group: I4/mcm) have been evaluated with density functional theory (DFT) calculations. [4] Analysis of the projected density of states (pDOS) of defective materials in comparison with pristine ones proved that the most likely vacancies, iodine and lead vacancies, can both generate shallow defect levels near the corresponding band gap edges or inside the bandgap. In conclusion, these preliminary results will pave the route to the better understanding of MAPI-based PSCs by establishing on solid scientific grounds the subtle relationships between the LHP fabrication methods, defectivity and ensuing electronic properties.