Lead-free 2D MASnBr 3 and Ruddlesden-Popper BA 2 MASn 2 Br 7 as light harvesting materials.

We have explored the structural, electronic, charge transport, and optical properties of lead-free 2D hybrid halide perovskites, MASnBr 3 and Ruddlesden-Popper perovskites, BAMASn 2 Br 7 monolayers. Under density functional theory (DFT) calculation, we applied mechanical strain, i.e. , tensile and compressive strain up to 10% in both cases. The mechanical strain engineering technique is useful for a tuned bandgap of 2D MASnBr 3 and 2D BAMASn 2 Br 7 . The calculated carrier mobility for the electron is 404 cm 2 V -1 s -1 and for the hole is up to 800 cm 2 V -1 s -1 for MASnBr 3 . For BAMASn 2 Br 7 the highest carrier mobility is up to 557 cm 2 V -1 s -1 for electrons and up to 779 cm 2 V -1 s -1 for the hole, which is 14% and 24% higher than the reported lead-iodide based perovskites, respectively. The calculated solar cell efficiency of 2D MASnBr 3 is 23.46%, which is 18% higher than the reported lead-based perovskites. Furthermore, the optical activity of the 2D MASnBr 3 and 2D BAMASn 2 Br 7 shows a high static dielectric constant of 2.48 and 2.14, respectively. This is useful to show nanodevice performance. Also, 2D MASNBr 3 shows a high absorption coefficient of 15.25 × 10 5 cm -1 and 2D BAMASn 2 Br 7 shows an absorption coefficient of up to 13.38 × 10 5 cm -1 . Therefore our theoretical results suggest that the systems are under mechanical strain engineering. This is convenient for experimentalists to improve the performance of the 2D perovskites. The study supports these materials as good candidates for photovoltaic and optoelectronic device applications.