Nanomaterials are expected to play an important role in the development of sustainable products. The use of nanomaterials in solar cells has the potential to increase their conversion efficiency. In this study, we performed a life cycle assessment (LCA) for an emerging nanowire‐based solar technology. Two lab‐scale manufacturing routes for the production of nanowire‐based solar cells have been compared—the direct growth of GaInP nanowires on silicon substrate and the growth of InP nanowires on native substrate, peel off, and transfer to silicon substrate. The analysis revealed critical raw materials and processes of the current lab‐scale manufacturing routes such as the use of trifluoromethane (CHF3), gold, and an InP wafer and a stamp, which are used and discarded. The environmental performance of the two production routes under different scenarios has been assessed. The scenarios include the use of an alternative process to reduce the gold requirements—electroplating instead of metallization, recovery of gold, and reuse of the InP wafer and the stamp. A number of suggestions, based on the LCA results—including minimization of the use of gold and further exploration for upscaling of the electroplating process, the increase in the lifetimes of the wafer and the stamp, and the use of fluorine‐free etching materials—have been communicated to the researchers in order to improve the environmental performance of the technology. Finally, the usefulness and limitations of lab‐scale LCA as a tool to guide the sustainable development of emerging technologies are discussed.

Nanotechnology is an emerging technology with the potential to contribute towards sustainability. However, there are growing concerns about the potential environmental and human health impacts of nanomaterials. Clearly, nanomaterials have advantages and disadvantages, and a balanced view is needed to assess the overall benefit. The current "green and clean" claims of proponents of nanomaterials across different sectors of the economy are evaluated in this review study. Focusing on carbon emissions and energy use, we have reviewed 18 life cycle assessment studies on nanomaterials in the solar, energy, polymer, medical and food sectors. We find that the "green and clean" claims are not supported for the majority of the reviewed studies in the energy sector. In the solar sector, only specific technologies tend to support the "green and clean" claims. In the polymer sector, only some applications support the "green and clean" claims. The main findings show that nanomaterials have high cradle-to-gate energy demand that result in high carbon emissions. Synthesis of nanomaterials is the main contributor of carbon emissions in the majority of the studies. Future improvements in reducing parameter uncertainties and in the energy efficiency of the synthesis processes of nanomaterials might improve the environmental performance of nanotechnologies.

Purpose The goal of this study is to perform an ex-ante life cycle assessment (LCA) of the emerging gallium-arsenide nanowire tandem solar cells on silicon (GaAs/Si) and to provide a benchmark for the commercialization of the technology. The environmental impacts and energy payback time (EPBT) of the GaAs/Si modules are compared with those of the incumbent single-Si modules. Parameters and efficiencies most relevant to be optimized in order to commercialize the technology are identified and discussed. Methods Two production routes for GaAs/Si solar cells are being up-scaled: the growth of GaAs nanowires on a native substrate, peel-off, and transfer to a silicon substrate (transfer route) and the direct growth of GaAs nanowires on a silicon substrate with assistance of a silicon-dioxide (SiO 2) nanotube template (direct growth route). Two ex-ante LCAs for the different manufacturing routes and an LCA for the incumbent single-Si technology were conducted. Environmental impacts of the GaAs/Si technology were assessed and compared with the incumbent. Various scenarios regarding sensitive parameters and processes were modeled-such as modeling several industrial scale tools, the energy consumption of sensitive processes, the number of substrate reuses, the frequency of re-polishing the wafer, and benchmarking the scale of improvement of major impact drivers. Results and discussion The analysis showed that, if expected process efficiencies are achieved, a 28% efficient GaAs/Si module performs 5 to 20% better (transfer route) and 20 to 30% better (direct growth route, except the ozone depletion impact) compared with an 18% efficient single-Si module, for all impact categories assessed-climate change, land use, acidification, ozone depletion, freshwater, marine, terrestrial ecotoxicity, eutrophication, human toxicity, and photochemical oxidation. Critical hotspots identified include the use of gold, trifluoromethane (CHF 3), and a GaAs wafer. The EPBT of the GaAs/Si nanowire tandem module is in between 1.37 (expected process efficiencies achieved) and 1.9 years (worst case scenario), while the EPBT of the single-Si module is 1.84 years. Results can be considered as a benchmark for the successful commercialization of the technology. Conclusions If 28% efficient GaAs/Si nanowire tandem modules are developed, expected process efficiencies are achieved, and at least 100 reuses of the GaAs substrate (transfer route) are realized; then, the GaAs/Si modules perform better compared with an 18% efficient single-Si module for most impact categories assessed. Conclusions from the ex-ante LCA are conditional (if-then) and can be used as a benchmark, allowing to quantify the efficiencies that need to be achieved to commercialize the technology.

L'insolubilité des polyamides dans les solvants classiques a toujours été un frein à la détermination de leurs caractéristiques physico‐chimiques en solution.Les solvants les plus communément utilisés pour ce type d'étude sont l'acide formique, le phénol, le trifluoroéthanol, le m‐crésol.Si L'étude des polyamides 6 est possible dans ces solvants (1) (2) avec cependant de nombreuses difficultés (3), les polyamides 11 et 12 se prêtent mal à l'étude par chromatographie sur gel d'une part à cause de leur insolubilité dans le trifluoroéthanol, d'autre part à cause de leur incrément d'indice nul ou faible dans le méta‐crésol.Dans ce travail, nou montrons que l'hexaméthylphosphorotriamide est un solvant parfaitement adapté et facile à utiliser pour la chromatographie de partage en phase liquide (GPC). Comme ce produit est aussi un excellent solvant du polystyréne, il est possible d'étalonner l'appareil à partir d'étalons de polystyrène. On montre enfin que ce solvant est utilisable pour de nombreux autres types de polymére.

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