Table C1
Key parameters and assumptions applied in EoL modelling of perovskite/Si tandem modules.
| Material | R1a | R2b | Cut-off with economic allocationc | Open-loop allocation | CFFe | ||
|---|---|---|---|---|---|---|---|
| Ae ca | Aopen-loopd | ACFF | Qsin/Qp | Qsout/Qp | |||
| Al | 74% | 97%ba | 0.73ca | 0.8 | 0.2 [15] | 1 [15] | 1 [15] |
| Glass | 0% | 93% [38] | 0.5 | 0.2 [15] | 1 [15] | 1 [15] | |
| Cu (cables) | 20% | 100% [38] | 0.5 | 0.2 [15] | 1 [15] | 1 [15] | |
| Cu (interconnection) | 20% | 76% [38] | 0.8 | 0.2 [15] | 1 [15] | 1 [15] | |
| Ag | 8% | 100% [38] | 1 | 0.2 | 1 [15] | 1 [15] | |
| Si (2N) | 0% | 54%bb | 1 | 0.5 | 1 | 1 | |
| Lead | 55% | 99% [21] | 0.8 | 0.5 | 1 | 1 | |
aThe recycled content ratio R1 means the share of recycled material in each input material. The value of each material is assumed based on the data of market mix in the Ecoinvent database [32], which reflects the level of market average.
bThe recovery rate of R2 is the ratio between the recovered material and the material used for the manufacturing. The value of each material is assumed based on the PV recycling process in this study. The recovery rate represents the best that can be technically achieved currently.
baThe R2 of Al is assumed to be 97%. The Al frame could be fully recovered, but the secondary treatment of Al scrap leads to a final recovery rate of 97% for Al.
bbIn this study, around 98% of Si in the modules was assumed to be recovered, i.e. 0.025 kg of Si per kg of modules. Due to the loss of Si in the manufacturing, the Si consumed to produce 1 kg of tandem modules is 0.047 kg. Therefore, the R2 for Si was assumed to be 54%.c In the EoL treatment processes, the secondary treatment processes such like the Al refining are more related to the production of recycled material. The chemical treatment of the SHJ section and perovskite could be also considered as a secondary treatment of the silicon waste and glass waste respectively. Therefore, in this study, these treatment processes were excluded from the EoL stage of the tandem modules when modelling recycling by the approach of cut-off with economic allocation. The disassembly, delamination and the pyrolysis processes were allocated between the EoL of modules and the recyclable material, i.e. Al waste, copper scrap, waste glass and ferro-Si.
caThe allocation factor 0.73 is the share allocated for the PV modules. It was calculated based on the information in Table D1.
dThe allocation factor of open-loop allocation in this study is the ratio between the market price of the recycled material and virgin material. The value of Aopen-loop varies as the market price changes. In this study, the approximate values were assumed depending on the publicly available information [52–54]. The price of the recycled glass from PV after remelting is unknown due to the lack of downstream value chain. Whether the recycled glass could be reused as solar glass is not clear, and due to the traces of metal (e.g. Ti) doped in the glass, the usage of recycled glass would be limited. Therefore, a value of 0.5 was given to the recycled glass. The downstream value chain for the recycled Si is also unknown. However, as described in Appendix B, the purity of Si is higher than 2N, so the recycled Si could be sold at least at the same price as for 2N-Si. Therefore, a value of 1 was assumed for the recycled Si.
eThe ACFF, Qsin/Qp, Qsout/Qp of Al, Cu and glass in the approach of CFF could be found in the Annex C of the PEF guide. The ACFF of Ag is assumed to be 0.2 according to the description of factor in PEF. A default value of 0.5 was assigned to silicon and lead. Qsin/Qp and Qsout/Qp are assumed to be 1 for Ag, silicon and lead, as no specific quality degradation was found.
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