Tin based perovskite solar cells
A tin based perovskite solar cell is a special type of perovskite solar cell, where the lead is substituted by tin. It has a tin-based perovskite structure (ASnX3), where 'A' is a 1+ cation and 'X' is a monovalent halogen anion. The maximum solar cell efficiency reported was 6.4% for methylammonium tin iodide (CH3NH3SnI3), 5.73% for CH3NH3SnIBr2, 4.8% for formamidinium tin triiodide (FASnI3), and 2.02% for CsSnI3. The methylammonium tin iodide (CH3NH3SnI3) has a band gap of 1.2-1.3 eV.
Tin-based perovskite solar cells are still in the research phase and there are relatively few publications about them, compared to their counterpart, lead-based perovskite solar cells. This is mainly due to the instability of the 2+ oxidation state of tin (Sn2+) in methylammonium tin iodide (CH3NH3SnI3), which can be easily oxidized to the more stable Sn4+, leading to a process called self doping, where the Sn4+ acts as a p-dopant leading to the reduction in the solar cell efficiency.
The main advantage of tin-based perovskite solar cells that they are lead-free. There are environmental concerns with using lead-based perovskite solar cells in large-scale applications; one such concern is that since the material is soluble in water, and lead is highly toxic, any contamination from damaged solar cells could cause major health and environmental problems.
In spite of an earlier reported low efficiency, formamidinium tin triiodide may hold promise because, applied as a thin film, it appears to have the potential to exceed the Shockley–Queisser limit by allowing hot-electron capture, which could considerably raise the efficiency.
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