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News | Photovoltaic solar power
Perovskite/silicon tandem cell technologies are probably the future generation of photovoltaics. Made by stacking a top cell of perovskite material on top of a bottom cell of silicon, these tandems promise a higher conversion efficiency of the solar energy received, higher than the current standard of single-junction silicon cells, at a low additional cost.
Today, environmental impact assessment and life cycle analysis of technologies must guide research efforts towards cell and panel designs with minimal environmental impact. Yet, it is still very difficult to orientate this immature tandem technology, for which record efficiencies of around 30% have only been demonstrated on surfaces of the range of 1 cm², and which generally uses laboratory processes for the layer deposition. The lack of a reference framework integrating technological progress, resulting from the low TRL of tandem technology, combined with the non-existence of a life cycle inventory for the materials constituting the top cell layers, makes the environmental analysis particularly complex. This is due to the large number of materials explored for the making of the different new layers and the fact that there is no fixed process for their implementation.
The high variability of the data and results of the state of the art, amplified by a still too weak expertise of the community on environmental aspects, is not compatible with the requirements of life cycle assessment (LCA), which demands a low level of uncertainty and a high quality of data.
The economic and environmental integration of new technologies is a major focus of the R&D programs developed by the Institute for Energy Transition INES.2S. In this context, the CEA and its industrial partners have building up for several years been a series of tools and reference databases to support their technological developments and choices.
The ITE INES.2S has built up a database of reference inventories for the best performing potential top cell materials with deposition processes that can be transposed to an industrial scale.
To comply with LCA requirements, the reference inventory takes into account the quality of the data (recency, consistency, process scalable to large surfaces, absence of substitutes, waste specification, etc.). These reference data are integrated into the database already available at the Institute for silicon modules. An environmental analysis of a reference technology, a Perovskite / Heterojunction Silicon (PK/Si-HJT) tandem module, using the collected inventory data, was then carried out in comparison with other technologies already studied.
The results of the study show that the PK/Si-HJT tandem technology has a large potential to reduce environmental impacts compared to a standard module, due to its high efficiency. The addition of the top cell layers does not increase the environmental impact. The silicon in the bottom cell, given its Chinese origin, is the main contributor to the overall impact. Manufacturing these tandem modules in Europe, starting from silicon, will therefore be a key element in reducing greenhouse gas emissions by more than 80% for this technology.
Environmental comparison Analysis of tandem technologies to standard silicon technologies
This work is ongoing, with the database being constantly enriched with other alternative layer materials and manufacturing processes. It will enable the setting up of a parameterized model for the environmental analysis of different tandem cell architectures.
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.