Eco-friendly lead-free and low-lead perovskite solar cells

Perovskite solar cells (PSCs) have attracted significant attention due to their rapid improvements in power conversion efficiency (PCE). However, the environmental hazards of lead-containing perovskites have intensified the need for lead-free alternatives. This review summarizes recent advances in lead-free and low-lead PSCs, focusing on material design, performance optimization, and stability enhancement. We first examine tin (Sn)-based perovskites, the most extensively studied lead-free system. Despite achieving PCEs up to 18%, their practical deployment is limited by Sn²⁺ oxidation, high background carrier density, and restricted long-term stability. Tin-lead (Sn–Pb) mixed perovskites are then discussed as a low-lead strategy that balances environmental safety with high performance, achieving certified efficiencies exceeding 24% for single-junction cells and over 28% in tandem devices. Other metal-based and double perovskites are also reviewed, with attention to their electronic structure limitations and potential optimization strategies. Finally, we highlight the key challenges and future directions. Commercialization remains constrained by issues including material stability, bandgap tuning, and scalable fabrication. This review provides a comprehensive framework for guiding the development of efficient, stable, and environmentally benign lead-free PSCs.