The target of this project is the establishment of a technology platform for the fabrication of a new generation of multi-junction photovoltaic cells based on nanostructured InGaN layers synthesized on silicon substrates. Currently, the photovoltaic market is dominated by single-junction crystalline silicon modules because of their low cost and long-term reliability. However, higher conversion efficiencies are obtained using advanced multi-junction techniques operating under concentration. In this context, this project aims at a major break-through in the solar domain by introduction of InGaN-on-Si solar cells. The ultimate objective is to implement a tandem cell with an InGaN junction in series with a silicon solar cell, in order to achieve a photovoltaic device with high conversion efficiency at a moderate production cost. Furthermore, the outstanding physical and chemical stability of III-nitrides enables them to operate in harsh environments, showing high stability under concentration conditions and superior resistance to high-energy particle radiation. We propose a completely new approach to the nitride-based solar cell, addressing directly nitrogen-polar high-In content layers on low-cost Si(111) substrates. The project must face a number of technological challenges: new state-of-the-art for nitride material design, growth and fabrication technology adapted to the InGaN specificities. As relevant novelties, three novel approaches are incorporated into the solar cells design: (i) growth of N-polar material by introducing a new concept of 3D buffer layer to improve the carrier collection, (ii) incorporation of InGaN/GaN nanostructures (quantum wells/dots) in the active region to enhance indium incorporation, facilitate the strain management and increase the spectral response in the infrared spectral range, and (iii) incorporation of heterostructured p-type region.