Tin‐Based Lead‐Free Perovskite Solar Cells: Mechanisms, Materials, and Device Engineering

ABSTRACT Perovskite solar cells (PSCs) have emerged as one of the most promising photovoltaic technologies due to their exceptional optoelectronic properties, low‐cost fabrication, and rapidly rising power conversion efficiency. Despite the impressive performance of lead‐based perovskites, concerns about lead toxicity and environmental instability have spurred intense efforts to develop lead‐free alternatives. Among these, tin (Sn)‐based perovskite solar cells (TPSCs) have shown great potential as eco‐friendly candidates owing to their suitable bandgap and comparable charge‐transport properties. However, the intrinsic instability of Sn 2+ , rapid oxidation to Sn 4+ , and poor film morphology continue to limit their efficiency and long‐ term operational stability. This review systematically explores the unique properties of Sn‐based perovskite materials, the widely used electron‐ and hole‐transport materials in device architectures, and the underlying degradation mechanisms that limit their performance. Furthermore, this review discussed recent progress and emerging strategies aimed at addressing the intrinsic instability of tin‐based systems. Overall, this review provides insights into achieving efficient, stable, and environmentally sustainable 100% lead‐free TPSCs.