Researchers have developed a method to create durable and efficient formamidinium lead iodide (FAPbI₃) solar cells using two-dimensional (2D) perovskite templates. By using specific 2D perovskites with formamidinium (FA) as the cation, they were able to form a stable black phase of FAPbI₃ at a lower temperature than usual. This approach results in a high-performance solar cell with an efficiency of 24.1% and exceptional durability under high-temperature and high-light conditions. The study shows that the 2D perovskite templates help stabilize the black phase of FAPbI₃, which is more stable and efficient than the yellow phase. The 2D perovskite templates are chosen based on their lattice parameters, which are nearly identical to those of the 3D FAPbI₃. This lattice matching allows for the formation of a stable interface, which enhances the crystallinity and stability of the FAPbI₃. The researchers used a combination of 2D perovskite templates and solution-processing techniques to create the FAPbI₃ films. The 2D perovskite templates were added to the precursor solution before the film was annealed, which helped in the formation of the black phase. The resulting films exhibited a bandgap of 1.48 eV and showed excellent performance under various conditions. The study also highlights the importance of the 2D perovskite templates in stabilizing the black phase of FAPbI₃. The 2D perovskite templates help in reducing the lattice disorder and improving the crystallinity of the FAPbI₃ films. This results in a more efficient and durable solar cell. The researchers demonstrated that the 2D perovskite templates can be used to create a stable and efficient FAPbI₃ solar cell with a high power conversion efficiency. The solar cells were tested under various conditions, including high temperatures and high light intensity, and showed excellent performance and stability. Overall, the study presents a novel approach to creating durable and efficient FAPbI₃ solar cells using 2D perovskite templates. This method has the potential to significantly improve the performance and stability of perovskite solar cells, making them more viable for commercial applications.Researchers have developed a method to create durable and efficient formamidinium lead iodide (FAPbI₃) solar cells using two-dimensional (2D) perovskite templates. By using specific 2D perovskites with formamidinium (FA) as the cation, they were able to form a stable black phase of FAPbI₃ at a lower temperature than usual. This approach results in a high-performance solar cell with an efficiency of 24.1% and exceptional durability under high-temperature and high-light conditions. The study shows that the 2D perovskite templates help stabilize the black phase of FAPbI₃, which is more stable and efficient than the yellow phase. The 2D perovskite templates are chosen based on their lattice parameters, which are nearly identical to those of the 3D FAPbI₃. This lattice matching allows for the formation of a stable interface, which enhances the crystallinity and stability of the FAPbI₃. The researchers used a combination of 2D perovskite templates and solution-processing techniques to create the FAPbI₃ films. The 2D perovskite templates were added to the precursor solution before the film was annealed, which helped in the formation of the black phase. The resulting films exhibited a bandgap of 1.48 eV and showed excellent performance under various conditions. The study also highlights the importance of the 2D perovskite templates in stabilizing the black phase of FAPbI₃. The 2D perovskite templates help in reducing the lattice disorder and improving the crystallinity of the FAPbI₃ films. This results in a more efficient and durable solar cell. The researchers demonstrated that the 2D perovskite templates can be used to create a stable and efficient FAPbI₃ solar cell with a high power conversion efficiency. The solar cells were tested under various conditions, including high temperatures and high light intensity, and showed excellent performance and stability. Overall, the study presents a novel approach to creating durable and efficient FAPbI₃ solar cells using 2D perovskite templates. This method has the potential to significantly improve the performance and stability of perovskite solar cells, making them more viable for commercial applications.