Physics:Tin-based perovskite solar cells

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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 methylammonium tin triiodide (CH3NH3SnI3) has a band gap of 1.2–1.3 eV, while formamidinium tin triiodide has a band gap of 1.4 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+,[1] leading to a process called self doping,[2] where the Sn4+ acts as a p-dopant leading to the reduction in the solar cell efficiency.

The maximum solar cell efficiency reported is 6.4% for methylammonium tin iodide (CH3NH3SnI3),[3] 5.73% for CH3NH3SnIBr2,[4] 2.02% for CsSnI3.[5] and above 9% for formamidinium tin triiodide (CH(NH2)2SnI3).[6][7]

The main advantages of tin-based perovskite solar cells are that they are lead-free and that can help to further tune the band-gap of the active layer. There are environmental concerns with using lead-based perovskite solar cells in large-scale applications;[8][9] 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.[10][11]

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.[12]

References

  1. Lee, S.J., et al., "Fabrication of Efficient Formamidinium Tin Iodide Perovskite Solar Cells through SnF2-Pyrazine Complex". Journal of the American Chemical Society, 2016.14.
  2. Takahashi, Y., et al., "Charge-transport in tin-iodide perovskite CH3NH3SnI3: origin of high conductivity". Dalton Transactions, 2011. 40(20): pp. 5563–p-5568.
  3. Noel, N.K., et al., "Lead-free organic–inorganic tin halide perovskites for photovoltaic applications". Energy & Environmental Science, 2014. 7(9): pp. 3061–3068.
  4. Hao, F., et al., "Lead-free solid-state organic-inorganic halide perovskite solar cells". Nature Photonics, 2014. 8(6): pp. 489–494.
  5. Kumar, M.H., et al., "Lead-Free Halide Perovskite Solar Cells with High Photocurrents Realized Through Vacancy Modulation". Advanced Materials, 2014. 26(41): pp. 7122–7127.
  6. Shuyan Shao, Jian Liu, Giuseppe Portale, Hong‐Hua Fang, Graeme R. Blake, Gert H. ten Brink, L. Jan Anton Koster, Maria Antonietta Loi (2018). "Highly Reproducible Sn‐Based Hybrid Perovskite Solar Cells with 9% Efficiency". Advanced Energy Materials 8 (4): 1702019. doi:10.1002/aenm.201702019. 
  7. Efat Jokar, Cheng-Hsun Chien, Cheng-Min Tsai, Amir Fathi, and Eric Wei-Guang Diau, "Robust Tin-Based Perovskite Solar Cells with Hybrid Organic Cations to Attain Efficiency Approaching 10%" Adv. Mat. 1804835 (2018)doi:10.1002/adma.201804835.
  8. Espinosa, N., et al., "Solution and vapour deposited lead perovskite solar cells: Ecotoxicity from a life cycle assessment perspective". Solar Energy Materials and Solar Cells, 2015. 137: pp. 303–310.
  9. Zhang, J., et al., "Life Cycle Assessment of Titania Perovskite Solar Cell Technology for Sustainable Design and Manufacturing". ChemSusChem, 2015. 8(22): pp. 3882–3891.
  10. Benmessaoud, I.R., et al., "Health hazards of methylammonium lead iodide based perovskites: cytotoxicity studies". Toxicology Research, 2016.
  11. Babayigit, A., et al., "Assessing the toxicity of Pb-and Sn-based perovskite solar cells in model organism Danio rerio". Scientific Reports, 2016. 6: p. 18721.
  12. Fang, Hong-Hua; Adjokatse, Sampson; Shao, Shuyan; Even, Jacky; Loi, Maria Antonietta (January 16, 2018). "Long-lived hot-carrier light emission and large blue shift in formamidinium tin triiodide perovskites". Nature Communications 9 (243): 243. doi:10.1038/s41467-017-02684-w. PMID 29339814. Bibcode2018NatCo...9..243F.