| Substrate |
Glass |
Excellent thermal stability |
Rigid |
Highly compatible with mechanical recycling |
| Strong barrier against moisture and chemicals |
Relatively expensive |
Can be integrated into existing silicon PV recycling streams |
| Polymers (PET, PEN) |
Flexible and lightweight |
Poor heat resistance |
Recycling is challenging under harsh thermal/chemical treatments |
| Lower cost |
Brittle under stress |
| Transparent conducting electrode |
FTO (fluorine-doped tin oxide) |
Good thermal stability |
Higher surface roughness |
Durable and less prone to degradation during recycling |
| Cost-effective |
| ITO (indium-doped tin oxide) |
Smooth surface |
Lower thermal stability |
Recycling is critical to recover indium, a scarce raw material |
| High optical transparency |
Expensive |
| ETL (electron transport layer) |
Inorganic (TiO2, SnO2, ZnO) |
Stable |
Strong adhesion to substrates complicates separation |
Difficult to recycle due to tight bonding with substrates |
| Low-cost |
| Easy fabrication |
| Organic (PCBM) |
Low processing temperature |
Poor stability |
Degrades under heat/solvent exposure |
| Low electron mobility |
Removal requires toxic solvents (e.g., chlorobenzene) |
| HTL (hole transport layer) |
Inorganic (NiOx, CuSCN) |
Chemically and thermally stable |
Possible interfacial reactions |
Strong adhesion reduces recyclability |
| Cost-effective |
| Organic (PEDOT: PSS, spiro-OMeTAD, PTAA) |
Solution-processable |
High cost |
Dopants complicate chemical separation during recycling |
| Enhanced charge transport |
Complex synthesis, poor long-term stability |
| Perovskite layer |
Pb-based |
High efficiency |
Toxicity concerns |
Pb recovery is essential to prevent environmental contamination |
| Tin-based |
Non-toxic |
Easily oxidized |
Oxidation complicates recovery and reuse |
| Air instability |
| Bismuth-based |
Stable |
Low efficiency |
Recycling pathways are not yet established |
| Low toxicity |
Early-stage technology |
| Back electrode |
Gold (Au) |
Excellent conductivity |
Very expensive. Requires vacuum deposition |
Can be selectively etched and recovered |
| High work function |
| Silver (Ag) |
Lower cost than gold |
Diffusion into perovskite |
Recoverable, but diffusion complicates separation |
| Requires vacuum deposition |
| Copper (Cu) |
Low cost |
Prone to oxidation |
Residual halides contaminate copper during recycling |
| Good conductivity |
| Carbon (C) |
Cheap |
Low work function |
Difficult to isolate during recycling |
| Chemically inert |
