The solar photovoltaic (PV), due to the huge abundance of the source, the low CO2 emissions on the life cycle, the competitive cost of production in comparison with energy sources based on fossil fuels, is taking on the leading role in the development of an electricity system de-carbonized that allows to reduce greenhouse gas emissions in order to contrast global warming. The development of next-generation PV technologies based on innovative materials and device architectures can represent a crucial node in addressing one of the challenges of the European Green Deal, namely eliminating greenhouse gas emissions by 2050. The project aims to study innovative materials that can contribute to the development of a high-efficiency PV technology, reliable over time and that uses sustainable raw materials free from availability problems. Materials will be developed to be used for a new generation of tandem solar cells, an architecture where two cells, each designed to effectively absorb a spectral region of solar radiation, are connected, minimizing losses due to thermalization and sub-bandgap. Materials (absorbers and selective contacts) for perovskite and silicon heterojunctions will be studied with the goal of designing and manufacturing perovskite/silicon and perovskite/perovskite tandem solar cells. The materials will also be selected in consideration of the possibility of overcoming some critical issues currently present in the emerging technology of perovskites and in Si heterojunction cells. As for perovskite, hybrid organic-inorganic films with various formulations have been used to make solar cells both at single junction and tandem junction with high efficiencies, but, in view of a potential industrial application of this technology, doubts related to the use of lead and organic groups must be dispelled due to their possible effects respectively on human health and stability over time of devices. Therefore, inorganic perovskites, perovskites without or with reduced lead content, and more generally perovskite films with different bandgaps will be developed with the aim of realizing tandem devices in combination with silicon cells or perovskite/perovskite tandem cells. To do this, alongside the study of the absorbers, it will be necessary to evaluate the appropriate charge carrier materials and strategies to improve the interfaces between perovskite and charge carriers. As for Si heterojunction cells, we will evaluate materials for highly transparent selective contacts, alternative to doped silicon films deposited by PECVD, with the aim of minimizing parasitic optical absorptions in the cell and evaluating less expensive deposition techniques with reduced safety problems for production processes. Transparent and conductive materials will then be evaluated for the front contact of the devices with the aim of reducing the use of scarcely available elements, such as the indium contained in the indium tin oxide commonly used in the cells. The main objectives of the project: the study of perovskite films with various chemical formulations (inorganic, without or with reduced lead content, low-dimensional perovskite) with different bandgaps to be used in PV devices; the study of charge carriers, of transparent contacts, also obtained with two-dimensional materials, and of interfaces between the various layers of the cells; the realization of a new generation perovskite/perovskite, perovskite/silicon tandem cells and the design of a research system for the vacuum deposition of tandem cells useful for defining a subsequent experimentation starting from the knowledge gained in the project.