The commercialization of halide perovskites is heavily constrained by the toxicity of lead, particularly under strict European frameworks like the RoHS directive for consumer electronics and the Safe and Sustainable by Design (SSbD) framework, where lead triggers the H1 hazard criterion as a Substance of Very High Concern (SVHC). While replacing lead with alternative cations (e.g., Sn, Bi, Sb, Ge, Cs) is a major research driver, achieving true sustainability requires looking beyond power conversion efficiency (PCE) and simple material substitution. This work evaluates the holistic sustainability of lead-free perovskite devices by addressing critical chemical, methodological, and supply chain challenges:

• Toxicity and the SSbD Framework: While elements like Bi and Cs show lower acute toxicity than lead, recent toxicological research indicates that other essential precursors (e.g., SnI₂, FAI, MAI) and standard processing solvents like DMF (also flagged under the SSbD H1 criterion) pose significant hazards that must be mitigated through green solvent alternatives.
• LCA Methodological Gaps: Current Life Cycle Assessment (LCA) characterization factors (e.g., USEtox) lack comprehensive human toxicity metrics for emerging substitutes. This introduces severe risks when comparing lead-based and lead-free alternatives, demanding a rigorous update of LCA characterization factors aligned with recent toxicological data.
• Raw Material Criticality: The transition to lead-free alternatives shifts the burden toward materials like Sb, Bi, and Ge, which are listed as critical raw materials by the EU, alongside potentially critical elements like Cs.
• Circular Economy and Device Architecture: End-of-Life (EOL) management via low-energy recycling and remanufacturing is essential to prevent metal leaching and recover high-value critical materials.

Furthermore, as the absorber layer's direct environmental impact is often secondary to that of transparent conductive substrates (TCS) and noble metal electrodes, optimizing the whole device stack is key to scalability.

Ultimately, while improving PCE and operational lifespans remains paramount to lowering the cradle-to-grave environmental footprint, ensuring the market readiness of next-generation lead-free optoelectronics requires a parallel commitment to circularity, non-hazardous design, and robust sustainability metrics.