Improving the performance of lead-free perovskite solar cells

Lead-halide perovskite solar cells (PSCs) have emerged as promising candidates for next-generation photovoltaics, yet the toxicity of lead poses a significant challenge to their sustainable development. Lead-free analogues, although exhibiting electronic structures and bandgap characteristics distinct from those of Pb-based perovskites, have demonstrated promising optoelectronic properties and improved stability, making them attractive candidates for next-generation photovoltaic applications. This review systematically examines a range of lead-free alternatives, including perovskites derived from isovalent or aliovalent substitution of lead, chalcogenide-based perovskite analogues, and metal-free organic perovskite systems. Recent advances in enhancing power conversion efficiency (PCE) through synergistic material design and device architecture optimization are highlighted. Beyond summarizing recent progress, this review provides a comparative perspective across different lead-free material families by correlating their electronic structures, defect-tolerance characteristics, photovoltaic performance, and sustainability considerations. Such a cross-material analysis reveals the fundamental factors governing device performance, identifies the distinct advantages and limitations of each material class, and provides insights into material-selection strategies for future photovoltaic development. Finally, we discuss the underlying origins of the performance gap between lead-based and lead-free PSCs and offer forward-looking perspectives on the cross-disciplinary approaches needed to overcome existing efficiency and stability bottlenecks. Lead-halide perovskites are promising, but their toxicity limits use; lead-free versions offer improved stability and solid performance. Here, the authors highlight lead-free alternatives and strategies to improve efficiency and stability in perovskite solar cells.