Development and optimization of photovoltaic devices is nowadays a topic of intense research. More than 13,000 research articles, published only between 2020 and 2023 are available on the Web of Knowledge database with the tag ‘photovoltaics’. Moreover, the market size of photovoltaic industry was estimated to more than 150 G$ in 2020, thus actively contributing to job creation. Among the variety of technologies available at this moment, one of the most promising is that of silicon / perovskite tandem solar cells. In a period of less than 10 years (2015 – 2023), conversion efficiencies higher than 30 % (1 cm²), therefore higher than the practical limit of numerous single junction technologies have been demonstrated by several laboratories worldwide.

Nevertheless, fabrication of such devices, which are composed by several layers, with thicknesses varying from one to hundreds of nanometers, is a complex process that relies on diverse deposition techniques. Moreover, cost constraints impose deposition on surfaces with micrometric texturing, for which low-TRL top cell deposition techniques are not fully adapted yet. For two-terminal technology, electrical interconnection is done through the recombination junction, responsible of optically and electrically coupling both subcells, respecting the design constraints previously mentioned. It has to fulfil efficient recombination of majority carriers left at the central part of the device after separation / extraction that takes place within each subcell. It is this topic that this thesis work is focused on.

This thesis work is developed in four main stages: first, optimization of a tunnel recombination junction, with p-i-n polarity considering optical, electrical and chemical interactions with top cell components, chosen in accordance with state of the art and successively deposited in collaboration with partner institutions. All these layers are deposited by industry-compatible techniques. Second, electrical characterization of these interconnection layers, with special attention on the transport mechanisms that can potentially limit carriers conductions through layers or interfaces. The choice and development of test vectors, adapted to this objective are also addressed. Third, optical, chemical and electronic characterization of chosen layers, using test vectors as close to functional devices as possible, with the aim of determining the layers and properties potentially limiting the stack performance, both as a consequence of their deposition on the bottom cell, as much as their influence on deposition of the top cell. Fourth, integration of promising materials and interconnection configurations in tandem devices is proposed, evaluating their performance and relationship of bottlenecks with characterization results previously obtained. Perspectives for the improvement on fabrication processes of test devices, as well as limitations actually observed will be finally presented and discussed, proposing directions for the continuation of this research work.