Lead‐Less Halide Perovskite Solar Cells

The rise and commercialization of perovskite solar cells (PSCs) is hindered by the toxicity of lead present in the perovskites used as the solar light absorber. To counter this problem, lead (Pb) can be fully (lead‐free) or partially (lead‐less) replaced by diverse elements. The former compounds suffer from poor efficiency and poor stability, whereas the later appear more promising. Herein, a survey of the methods reported in the literature to reduce Pb content in PSCs to fabricate “lead‐less” (also called “lead‐deficient”) PSCs is offered. First, the comparison of Sn and Pb elements and the partial replacement of Pb by Sn are developed. Then, its substitution by either Ge, Sr, or other alkaline‐earth‐metals, transition metals, and elements from columns 12, 13, and 15 of the periodic table are detailed. The new families of perovskites based on the insertion of organic cations to replace lead and halogen units, namely the “lead‐deficient” and “hollow” halide perovskites are then presented and discussed. Finally, atypical ways to reduce the toxicity of PSCs are presented: perovskite layer thickness reduction via optimization of photon collection, integration of photonic structures, and usage of recycled lead. The current achievements and the outlook of those strategies are presented and discussed.