Coordination Nanosheets Stabilizing Efficient Tin-Based Perovskite Solar Cells

Tin-based perovskites, characterized by their advantageous bandgap and much lower toxicity, have emerged as a promising alternative to lead-based perovskites in solar cell applications. However, the efficiency and stability of tin-based perovskite solar cells (Sn-PSCs) are still limited by defects resulting from the easy oxidation of Sn²⁺ to Sn⁴⁺. Herein, an approach to enhance the optoelectronic performance of Sn-PSCs by incorporating terpyridine-zinc(II) (ZnTPY) coordination nanosheets (CONASHs), synthesized via liquid-liquid interfacial polymerization, into tin-based perovskites is delivered. Following physical fragmentation, ZnTPY CONASHs, enriched with unsaturated terpyridine groups, undergo multidentate chelation with SnI₂, forming ZnTPY:SnI₂ heterogeneous nuclei. This process effectively enhances the crystallization of tin-based perovskites while mitigating recombination and defect chemistry related to Sn²⁺ oxidation. As a result of superior crystal quality, the ZnTPY CONASHs-modified tin perovskite exhibits a longer photoluminescence lifetime. Consequently, the Sn-PSC incorporating ZnTPY complex achieves a power conversion efficiency of 11.59%, compared to 9.14% for the control device, along with improved operational stability with encapsulation. Thus, this work underscores the critical role of coordination nanosheets for regulating coordination in the precursor solution to achieve high-quality tin-based perovskite films, offering a pathway to more efficient and stable Sn-PSCs.