Work package 1: During the reporting period, the project made significant progress in developing high-efficiency nanowire-based multi-junction photovoltaic devices. Nanowire composition and doping were systematically optimized by varying precursor flows (TMIn, TMGa, PH3 and AsH₃) to achieve desired InAsP and GaInP bandgaps. Several methods and attempts to surface passivation of the nanowires were tested and evaluated, with the purpose to enhance optical and electronic performance.
Work package 2: Significant progress was made in wireless power transmission (WPT) systems for space applications. System-level design and high-frequency device-level implementation advanced beyond conventional systems. Satellite-to-satellite WPT specifications were defined, complemented by modelling alternative lower-frequency configurations. ULUND fabricated the first batch of nanowire-based transistors using a refined process with field-plate modules, achieving precise nanoscale control (50 nm gate and field plate lengths) and confirming structural integrity via SEM analysis. These developments integrate high-frequency WPT design with precision nanowire transistor fabrication, enabling compact, efficient, and scalable in-space energy transfer.
Work Package 3 focused on upscaling nanowire solar cell technologies to 100 mm wafer-level fabrication. ULUND and UPV developed nanoimprint lithography (NIL) master stamps, optimized Si and SiN etching processes, and installed an Au electroplating system for precise large and selective area patterning of catalytic particles used for growth. Advanced characterization methods were established, including Electron Channeling Contrast Imaging (ECCI) for non-destructive defect mapping, complemented by backscattered electron and cathodoluminescence studies revealing correlations between Ga content and optical response.
Work Package 4 addressed testing, validation, and performance analysis of nanowire and tandem solar cells. ULUND, UMA, and Fraunhofer ISE conducted optical, electrical, and structural characterizations, including photoluminescence, electroluminescence, laser-beam-induced current, EQE, and solar simulator measurements. Fraunhofer ISE developed a cryostat-based system enabling low-temperature IV measurements (98–323 K) under varying irradiance, confirming temperature-dependent behaviour of the nanowire solar cells, comparable to state-of-the-art III–V cells.
Work Package 5 focused on sustainability through Life Cycle Assessment (LCA), decarbonization analysis, and Critical Raw Materials (CRM) assessment. A literature review highlighted gaps in existing LCA data for nanowire photovoltaics. A site visit to Lund University enabled collection of operational data from the MOVPE reactor, informing preliminary LCA models in SimaPro and guiding improvements in process efficiency and environmental impact.
Work package 8: NCSRD performed advanced simulations of optical absorption in single and tandem nanowire arrays, optimizing geometry for current matching. Using MULTEM and COMSOL, InP and GaInP/InP nanowire arrays were modeled, confirming alignment with experimental data. MULTEM provided significantly faster simulations, supporting efficient design iterations.
