Assessing the environmental and economic sustainability of emerging tandem photovoltaic technologies in China

• GaAs tandem has 2–5 times higher impacts than the perovskite tandem. • High material and energy consumption for GaAs wafer contributes most to the impacts. • By reusing GaAs wafer 100 times, most impacts are lower than for perovskite tandem. • GaAs tandem life cycle costs are around five times higher than the perovskite costs. • Arsine and gallium in the GaAs tandem account for ∼ 70 % of the total costs. Tandem cell technologies with high conversion efficiency are considered promising options for a future photovoltaics (PV) market. Several studies have assessed the environmental and economic impacts of tandem technologies in European countries; however, such studies are not available for China, the largest PV market in the world. To fill this research gap, this paper presents a comprehensive life cycle environmental and economic assessment of solar electricity in China generated by two emerging PV tandem technologies: 4-terminal gallium arsenide/silicon heterojunction (GaAs/SHJ) and perovskite/silicon with tunnel oxide passivated contact (PSC/TOPCon). The study uses life cycle assessment (LCA) to evaluate the environmental impacts and life cycle costing (LCC) to assess the economic aspects of both technologies as such studies are not available in the literature. The LCA results reveal that electricity from the GaAs/SHJ tandem PV (based on reusing GaAs wafer five times) has 2–5 times higher impacts than electricity from PSC/TOPCon in most of the 18 impact categories considered, owing to high material and energy consumption for GaAs manufacturing. For example, the climate change potential of the GaAs/SHJ system (127 kg CO 2 eq./MWh) is more than 3.5 times higher than that of PSC/TOPCon (33.5 kg CO 2 eq./MWh). However, if the GaAs wafer were reused 100 times, then the climate change and all other impacts of GaAs/SHJ would become lower (1–26 %) than those of PSC/TOPCon, except for metal depletion which would still be significantly (126 %) higher. The life cycle costs of electricity generation by GaAs/SHJ are also much higher (135 $/MWh) than those of PSC/TOPCon (23.7 $/MWh), with arsine and gallium accounting for 68 % of the total cost in the GaAs/SHJ system. As these two technologies are currently at an early stage of development, further developments to reduce the material and energy consumption, as well as improve the efficiency and recyclability of both systems, are essential for future cost-effective and low-impact solar electricity generation in China.