In this work a study about the behavior of nanomaterial-based innovative transparent electrodes is presented, with a special focus on graphene, for space photovoltaic applications, in particular their transparency and the efficiency of the final device. The efficiency of a solar cell is characterized by referring to Power Conversion Efficiency and External/Internal Quantum Efficiency. Starting from the literature results, it is possible to observe that solar cells realized by innovative nanomaterial-based transparent electrodes show promising results in terms of efficiency in the Earth environment. It is known that the space environment is characterized by extreme conditions including high-energy radiation, strong temperature variations and high vacuum, which can damage materials and, consequentially, influence their performances. Among all the properties like transmittance and sheet resistance, which are the main requirements for a good transparent electrode, could change their value and, therefore, influence the efficiency of the solar cell adopting this kind of electrode. In this paper, a theoretical analysis on the effects of high-energy radiation on the transmittance of graphene layers is given, leading to the observation that in the UV frequency range, it shows a sharp fall. Moreover, the effect of temperature varying is studied by an theoretical analysis on the resistivity of the twisted graphene bilayer. It is possible to observe that, in this configuration, the system moves from a superconductor to a metal, according to temperature and twist angle. This represents a starting point to have good efficiency of solar devices in a space environment by keeping high the transparency of their electrodes.

Multijunction solar cells employing a GaInP/GaAs/Ge triple-junction configuration are the dominant technology for space photovoltaic applications. The choice of an efficient electrode is crucial in solar cells, as it enables effective charge carrier collection and transport while allowing maximum light to reach the active layer. Indium tin oxide (ITO)/graphene hybrid electrodes have emerged as smart transparent conductors offering significant advantages over conventional brittle ITO films. Graphene electrodes were prepared by cold-wall chemical vapor deposition and ITO electrodes were commercially obtained and used as a base for hybrid ITO/graphene electrodes. Raman spectroscopy confirmed the successful integration and characteristic G and 2D bands on the ITO surface. Nanoscale current mapping via Tunneling Atomic Force Microscopy (TUNA-AFM) verified continuous conductive pathways throughout the film with ~60% increase in nanoscale tunneling current at graphene/ITO interfaces, indicating improved local charge transport pathways. These results demonstrate the suitability of ITO/graphene hybrid electrodes a promising material for multijunction solar cells and other aerospace technologies.