Bulk Defects Passivation of Tin Halide Perovskite by Tin Thiocyanate

Abstract

Despite the rapid efficiency increase, tin halide perovskite solar cells are significantly behind their lead-based counterpart, with the highest reported efficiency of 15.38%. The main reason for this large difference is attributed to the instability of Sn²⁺, which easily oxidizes to Sn⁴⁺, creating Sn vacancies and increasing the open-circuit voltage loss. In this work, we implemented tin thiocyanate (Sn(SCN)₂) as an additive for passivating the bulk defects of a germanium-doped tin halide perovskite film. Adding Sn²⁺ and SCN⁻ ions reduces the Sn and iodine vacancies, limiting non-radiative recombination and favoring longer charge-carrier dynamics. Moreover, the addition of Sn(SCN)₂ induces a higher film crystallinity and preferential orientation of the (l00) planes parallel to the substrate. The passivated devices showed improved photovoltaic parameters with the best open-circuit voltage of 0.716 V and the best efficiency of 12.22%, compared to 0.647 V and 10.2% for the reference device. In addition, the passivated solar cell retains 88.7% of its initial efficiency after 80 min of illumination under 100 mW cm^-2 and is substantially better than the control device, which reaches 82.6% of its initial power conversion efficiency only after 30 min. This work demonstrates the passivation potential of tin-based additives, which combined with different counterions give a relatively large space of choices for passivation of Sn-based perovskites.

Keywords

additives / solar cells / tin halide perovskite / tin oxidation / tin thiocyanate / trap passivation

References

[1] Z. Liang, Y. Zhang, H. Xu, et al., “Homogenizing Out-of-Plane Cation Composition in Perovskite Solar Cells,” Nature 624, no. 7992 (2023): 557-563.

[2] NREL, “NREL Efficiency Chart,” 2024, https://www.nrel.gov/pv/cell-efficiency.html.

[3] G. Xing, N. Mathews, S. S. Lim, Y. M. Lam, S. Mhaisalkar, and T. C. Sum, “Long-Range Balanced Electron- and Hole-Transport Lengths in Organic-Inorganic CH₃NH₃PbI₃,” Science 6960 (October 2013): 498-500.

[4] A. Miyata, A. Mitioglu, P. Plochocka, et al., “Direct Measurement of the Exciton Binding Energy and Effective Masses for Charge Carriers in Organic-Inorganic Tri-Halide Perovskites,” Nature Physics 11, no. 7 (2015): 582-587.

[5] J. M. Ball, S. D. Stranks, M. T. Hörantner, et al., “Optical Properties and Limiting Photocurrent of Thin-Film Perovskite Solar Cells,” Energy & Environmental Science 8, no. 2 (2015): 602-609.

[6] B. Hailegnaw, S. Kirmayer, E. Edri, G. Hodes, and D. Cahen, “Rain on Methylammonium Lead Iodide Based Perovskites: Possible Environmental Effects of Perovskite Solar Cells,” Journal of Physical Chemistry Letters 6, no. 9 (2015): 1543-1547.

[7] The European Parliament and the Council of the European Union, “Directive 2011/65/EU of the European Parliament and of the Coucil of 8 June 2011 on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment,” Official Journal of the European Union 25 (2014): 1682-1690.

[8] A. Filippetti, S. Kahmann, C. Caddeo, et al., “Fundamentals of Tin Iodide Perovskites: A Promising Route to Highly Efficient, Lead-Free Solar Cells,” Journal of Materials Chemistry A 9, no. 19 (2021): 11812-11826.

[9] C. C. Stoumpos, C. D. Malliakas, and M. G. Kanatzidis, “Semiconducting Tin and Lead Iodide Perovskites With Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared Photoluminescent Properties,” Inorganic Chemistry 52, no. 15 (2013): 9019-9038.

[10] H. H. Fang, S. Adjokatse, S. Shao, J. Even, and M. A. Loi, “Long-Lived Hot-Carrier Light Emission and Large Blue Shift in Formamidinium Tin Triiodide Perovskites,” Nature Communications 9, no. 1 (2018): 243.

[11] W. Ke, C. C. Stoumpos, and M. G. Kanatzidis, “Unleaded” Perovskites: Status Quo and Future Prospects of Tin-Based Perovskite Solar Cells,” Advanced Materials 31, no. 47 (2019): 1803230.

[12] N. K. Noel, S. D. Stranks, A. Abate, et al., “Lead-Free Organic-Inorganic Tin Halide Perovskites for Photovoltaic Applications,” Energy & Environmental Science 7, no. 9 (2014): 3061-3068.

[13] F. Hao, C. C. Stoumpos, D. H. Cao, R. P. H. Chang, and M. G. Kanatzidis, “Lead-Free Solid-State Organic-Inorganic Halide Perovskite Solar Cells,” Nature Photonics 8, no. 6 (2014): 489-494.

[14] Y. Shi, Z. Zhu, D. Miao, Y. Ding, and Q. Mi, “Interfacial Dipoles Boost Open-Circuit Voltage of Tin Halide Perovskite Solar Cells,” ACS Energy Letters 9, no. 4 (2024): 1895-1897.

[15] H. Cao, Z. Zhang, M. Zhang, et al., “The Effect of Defects in Tin-Based Perovskites and Their Photovoltaic Devices,” Materials Today Physics 21 (2021): 100513.

[16] A. Toshniwal and V. Kheraj, “Development of Organic-Inorganic Tin Halide Perovskites: A Review,” Solar Energy 149 (2017): 54-59.

[17] M. Konstantakou and T. Stergiopoulos, “A Critical Review on Tin Halide Perovskite Solar Cells,” Journal of Materials Chemistry A 5, no. 23 (2017): 11518-11549.

[18] F. Hao, C. C. Stoumpos, P. Guo, et al., “Solvent-Mediated Crystallization of CH₃NH₃SnI₃ Films for Heterojunction Depleted Perovskite Solar Cells,” Journal of the American Chemical Society 137, no. 35 (2015): 11445-11452.

[19] B. B. Yu, Z. Chen, Y. Zhu, et al., “Heterogeneous 2D/3D Tin-Halides Perovskitesolar Cells With Certified Conversion Efficiency Breaking 14%,” Advanced Materials 33, no. 36 (2021): 2102055.

[20] K. Nishimura, M. A. Kamarudin, D. Hirotani, et al., “Lead-Free Tin-Halide Perovskite Solar Cells With 13% Efficiency,” Nano Energy 74 (2020): 104858.

[21] C. Wang, Y. Zhang, F. Gu, et al., “Illumination Durability and High-Efficiency Sn-Based Perovskite Solar Cell Under Coordinated Control of Phenylhydrazine and Halogen Ions,” Matter 4, no. 2 (2021): 709-721.

[22] G. Liu, Y. Zhong, W. Feng, et al., “Multidentate Chelation Heals Structural Imperfections for Minimized Recombination Loss in Lead-Free Perovskite Solar Cells,” Angewandte Chemie International Edition 61, no. 40 (2022): e202209464.

[23] X. Meng, Y. Wang, J. Lin, et al., “Surface-Controlled Oriented Growth of FASnI₃ Crystals for Efficient Lead-Free Perovskite Solar Cells,” Joule 4, no. 4 (2020): 902-912.

[24] S. Shao, J. Liu, G. Portale, et al., “Highly Reproducible Sn-Based Hybrid Perovskite Solar Cells With 9% Efficiency,” Advanced Energy Materials 8, no. 4 (2018): 170219.

[25] E. Jokar, C. H. Chien, C. M. Tsai, A. Fathi, and E. W. G. Diau, “Robust Tin-Based Perovskite Solar Cells With Hybrid Organic Cations to Attain Efficiency Approaching 10%,” Advanced Materials 31, no. 2 (2019): 1804835.

[26] E. Jokar, C. H. Chien, A. Fathi, M. Rameez, Y. H. Chang, and E. W. G. Diau, “Slow Surface Passivation and Crystal Relaxation With Additives to Improve Device Performance and Durability for Tin-Based Perovskite Solar Cells,” Energy & Environmental Science 11, no. 9 (2018): 2353-2362.

[27] K. Nishimura, D. Hirotani, M. A. Kamarudin, et al., “Relationship Between Lattice Strain and Efficiency for Sn-Perovskite Solar Cells,” ACS Applied Materials & Interfaces 11, no. 34 (2019): 31105-31110.

[28] F. Gu, S. Ye, Z. Zhao, et al., “Improving Performance of Lead-Free Formamidinium Tin Triiodide Perovskite Solar Cells by Tin Source Purification,” Solar RRL 2, no. 10 (2018): 1800136.

[29] N. Ito, M. A. Kamarudin, D. Hirotani, et al., “Mixed Sn-Ge Perovskite for Enhanced Perovskite Solar Cell Performance in Air,” Journal of Physical Chemistry Letters 9, no. 7 (2018): 1682-1688.

[30] C. H. Ng, K. Nishimura, N. Ito, et al., “Role of GeI₂ and SnF₂ Additives for Snge Perovskite Solar Cells,” Nano Energy 58 (2019): 130-137.

[31] J. W. Lee, S. H. Bae, N. De Marco, Y. T. Hsieh, Z. Dai, and Y. Yang, “The Role of Grain Boundaries in Perovskite Solar Cells,” Materials Today Energy 7 (2018): 149-160.

[32] P. Mandal, B. Show, S. T. Ahmed, D. Banerjee, and A. Mondal, “Visible-Light Active Electrochemically Deposited Tin Selenide Thin Films: Synthesis, Characterization and Photocatalytic Activity,” Journal of Materials Science: Materials in Electronics 31, no. 6 (2020): 4708-4718.

[33] W. Liao, D. Zhao, Y. Yu, et al., “Lead-Free Inverted Planar Formamidinium Tin Triiodide Perovskite Solar Cells Achieving Power Conversion Efficiencies up to 6.22%,” Advanced Materials 28, no. 42 (2016): 9333-9340.

[34] T. H. Chowdhury, Y. Reo, A. R. B. M. Yusoff, and Y. Y. Noh, “Sn-Based Perovskite Halides for Electronic Devices,” Advanced Science 9, no. 33 (2022): 2203749.

[35] F. Wang, X. Jiang, H. Chen, et al., “2D-Quasi-2D-3D Hierarchy Structure for Tin Perovskite Solar Cells With Enhanced Efficiency and Stability,” Joule 2, no. 12 (2018): 2732-2743.

[36] Y. Liao, H. Liu, W. Zhou, et al., “Highly Oriented Low-Dimensional Tin Halide Perovskites with Enhanced Stability and Photovoltaic Performance,” Journal of the American Chemical Society 139, no. 19 (2017): 6693-6699.

[37] Y. Jiang, Z. Lu, S. Zou, et al., “Dual-Site Passivation of Tin-Related Defects Enabling Efficient Lead-Free Tin Perovskite Solar Cells,” Nano Energy 103 (2022): 107818.

[38] S. Kahmann, S. Shao, and M. A. Loi, “Cooling, Scattering, and Recombination—The Role of the Material Quality for the Physics of Tin Halide Perovskites,” Advanced Functional Materials 29, no. 35 (2019): 1902963.

[39] C. Li, Z. Song, D. Zhao, et al., “Reducing Saturation-Current Density to Realize High-Efficiency Low-Bandgap Mixed Tin-Lead Halide Perovskite Solar Cells,” Advanced Energy Materials 9, no. 3 (2019): 1803135.

[40] Q. Jiang, Y. Zhao, X. Zhang, et al., “Surface Passivation of Perovskite Film for Efficient Solar Cells,” Nature Photonics 13, no. 7 (2019): 460-466.

[41] S. R. Cowan, A. Roy, and A. J. Heeger, “Recombination in Polymer-Fullerene Bulk Heterojunction Solar Cells,” Physical Review B 82, no. 24 (2010): 245207.

[42] T. Du, W. Xu, S. Xu, et al., “Light-Intensity and Thickness Dependent Efficiency of Planar Perovskite Solar Cells: Charge Recombination Versus Extraction,” Journal of Materials Chemistry C 8, no. 36 (2020): 12648-12655.

[43] T. Wu, X. Liu, X. Luo, et al., “Lead-Free Tin Perovskite Solar Cells,” Joule 5, no. 4 (2021): 863-886.

[44] M. Pitaro, E. K. Tekelenburg, S. Shao, and M. A. Loi, “Tin Halide Perovskites: From Fundamental Properties to Solar Cells,” Advanced Materials 34, no. 1 (2021): 2105844.

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