Solar cells are the preferred method for powering today’s satellites. The cell efficiency determines the available power and is hence of exceptional importance for any spacecraft equipment or system. Besides the efficiency that is directly linked to the solar array power (W/m2), solar cells define also further Key Performance Indicators such as specific mass (kg/m2) and manufacturing costs (EUR/W). The SiLaSpaCe proposal will address these needs by developing next generation, high performance, GaInP/GaInAs/Ge multi-junction space solar cells with reduced weight, high radiation stability and increased efficiency. This ambitious goal will be achieved by the introduction (spinning-in) of Si photovoltaic technologies which are absolutely new for space applications and which will lead to a disruptive development. These measures will furthermore allow the introduction of thinner Ge wafers and metamorphic top structures leading to increased efficiency and to reduced weight bringing GaInP/GaInAs/Ge multi-junction space solar cells significantly beyond the state-of the art which are lattice-matched GaInP/GaInAs/Ge triple-junction solar cells with a Beginning-of-Life (BOL) efficiency of 30%. In the SiLaSpaCe project GaInP/GaInAs/Ge multi-junction space solar cells shall reach a BOL efficiency of 33%. The proposal relates clearly to the EU call topic "H2020-LEIT-Space-Competitiveness of the European Space Sector-2015”. Its main objective is to preserve European independence and competitiveness in the space market by incorporating and developing a brand-new space solar cell technology. The proposal’s ambitious developments will enhance new and key enabling technologies (KET) like energy production, materials and structures as well as additive layer manufacturing techniques. Finally the proposal will attract terrestrial technologies to space systems and mobilises the new incorporation of non-space actors into the space landscape.

Crystalline silicon wafer solar cells have been dominating the photovoltaic market so far due to the availability and stability of c-Si and the decades of Si technology development. However, without new ways to improve the conversion efficiencies further significant cost reductions will be difficult and the c-Si technology will not be able to maintain its dominant role. In the SiTaSol project we want to increase conversion efficiencies of c-Si solar cells to 30 % by combining it with III-V top absorbers. Such a tandem solar cell will result in huge savings of land area and material consumption for photovoltaic electricity generation and offers clear advantages compared to today’s products. The III-V/Si tandem cell with an active Si bottom junction with one front and back contact is a drop-in-replacement for today’s Si flat plate terrestrial PV. To make this technology cost competitive, the additional costs for the 2-5 µm Ga(In)AsP epitaxy and processing must remain below 1 €/wafer to enable module costs <0.5 €/Watt-peak. It is the intention of the SiTaSol project to evaluate processes which can meet this challenging cost target and to proof that such a solar cell can be produced in large scale. Key priorities are focused on the development of a new growth reactor with efficient use of the precursor gases, enhanced waste treatment, recycling of metals and low cost preparation of the c-Si growth substrate. High performance devices will be demonstrated in an industrial relevant environment. The project SiTaSol approaches these challenges with a strong industrial perspective and brings together some of the most well-known European partners in the field of Si PV and III-V compound semiconductors. Furthermore SiTaSol will support the competitiveness of the European industry by providing innovative solutions for lowering manufacturing costs of III-V materials which are essential in today’s electronic products including laptops, photonic sensors and light emitting diodes.

Project RadHard aims for increasing both the technical and commercial competitiveness of the European space solar cell technology to maintain the independence of European space industry in this field. RadHard will demonstrate the future next generation of space solar cells featuring i) beginning-of-life efficiency exceeding 35% under AM0 condition enabled by a new, patent protected 4-junction space solar cell, ii) the world’s highest radiation hardness leading to an efficiency >31% after 1E15 cm-2 1MeV electron irradiation, iii) scaling of the solar cell manufacturing to 200mm wafer size to enable competitive cost of the product and iv) demonstration of manufacturability and reliability of this cell concept. TR levels for relevant technologies will be increased from TRL 3 to 5-6. The project makes use of technology innovations in solar cells design, epitaxy, semiconductor bonding and ultra large Ge wafers. The work plan is based on a parallel development of the new solar cell by semiconductor bonding and establishing solar cell manufacturing processes on 200 mm Ge wafers. At the end of the project, these development lines will be merged to demonstrate the commercial viability of the selected approach. Technology development activities will be accompanied by extensive test programme to allow for continuous feedback on the achieved device performance and to address reliability aspects. Finally an industrialization plan for the new 4-junction semiconductor bonded solar cell will be elaborated. The project team is led by AZUR SPACE and consists of 7 industrial partners (incl. 1 SME) and 2 academic institutes and covers all R&D aspects, from basic research on advanced materials at academic partners to device manufacturing in industrial environment and testing on higher integration level. The relevance of the team for commercial exploitation is extremely high: RadHard includes industrial partners from each of the main parts of the value chain for space solar generators.