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Max Marwede
Cycling critical absorber materials of CdTe- and CIGS-photovoltaics: Material efficiency along the life-cycle
Supervisor: Prof. Dr. Armin Reller [Resource Strategy]
Date of oral examination: 07/18/2013
104 pages, english , Opus Online
Chalcogenide (CdTe) and chalcopyrite (CIGS, CIS) photovoltaic (PV) production increased on average over a 100 %25 per year during the last decade. The used semiconducting compounds (II-VI, I-III-VI2 compounds and their quaternary and pentenary alloys) are especially suitable for solar cells due to their high absorption coefficient, their long-term stable performance and their fast processability. Due to their high absorption coefficient, very thin-layers (< 2 %B5m) are sufficient to absorb most of the useful spectrum of the light. However, used absorber materials such as indium (In) and tellurium (Te) are regarded as critical and their limited availability and their high costs can, to a certain extent, impede the deployment of those PV technologies. Therefore, this work analyses how efficiency measures along the life-cycle of CdTe- and CIGS-PV modules can reduce the net-demand for these materials. Efficiency measures include the decrease of the specific material content of the solar cell (i.e. amount of material per power), the decrease of the material input in production, the recycling of production waste, and the end-of-life recycling of PV modules. Several recycling technologies for CIGS- and CdTe-PV modules have been developed in the last years which recycle the thin-film materials. This work describes possible recycling paths based on proven recycling concepts. Afterwards it is estimated how much tellurium can potentially be recovered from CdTe-PV production and end-of-life waste to substitute for %93primary%94 tellurium. Then there is an assessment of how material efficiency measures along the module%92s life-cycle can reduce the net material demand for CIGS and CdTe solar modules and thus the material costs. The results show that recycling technologies are sufficiently explored and commercially available, although they are not yet economically viable (costs exceed revenues). Should Te be recycled from end-of-life modules, the CdTe-PV industry has the potential to fully rely on recycled Te as of 2038. This is possible because demand begins to decline after 2020 despite market growth due to efficiency measures during production and at product level. If end-of-life modules were to provide 20%25 of the production feedstock, and 60-85 %25 of the material feedstock is used, then the costs for the technical grade Te could increase by 260 %25 and indium 430 %25, respectively, and both technologies would still be competitive against crystalline silicon photovoltaics. However, in the long term the photovoltaic future might not rely on current critical materials but instead on low cost and more abundant materials such as iron pyrite or organics. Until then both CIGS- and CdTe-PV can support a high share of the photovoltaic market if the materials are used efficiently.