Understanding the differences between MABiI3 and MAPbI3 under an advanced Kelvin Probe system

Zubin Parekh^a, Conor Davidson^b, Matthew Davies^a, Iain Baikie^b, Sagar Jain^a

^aSPECIFIC, College of Engineering Swansea University, SPECIFIC, Baglan Bay Innovation Centre, Central Avenue, Baglan, Port Talbot, SA12 7AX, United Kingdom

^bKP Technology, Burn Street, Wick, Caithness, KW1 5EH, UK

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV19)

Roma, Italy, 2020 May 12th - 14th

Organizers: Prashant Kamat, Filippo De Angelis and Aldo Di Carlo

Poster, Zubin Parekh, 259
Publication date: 6th February 2020

The future of perovskite solar cells is bright. It could be even brighter with a serious lead-free competitor to methylammonium lead iodide (MAPbI₃). Methylammonium bismuth iodide (MABiI₃) is one of those perovskites that has potential to provide benefits over MAPbI₃; it is less toxic and atmospherically more stable [1][2][3][4].

This purpose of this study was to measure differences in semiconductor properties such as fermi level response to light, HOMO level and band gap. Comparing these characteristics highlights why MAPbI₃ has the superior PCE; a smaller band gap, and larger open circuit voltage under illumination was measured for MAPbI₃.

The work function response of MAPbI₃is 150mV larger than the response of MABiI₃ – this is a representative of a greater open circuit voltage achievable. Hence, MAPbI₃PCE values are commonly >15% [5][6] [7] whilst MABiI₃ PCE values are around 3% [8].

Surface photovoltage spectroscopy has revealed that MABiI₃experienced a work function decrease under low energy light (650-850nm) and a work function increase under high energy light (400-600nm). MABiI₃has complex activity under illumination. An understanding of the immediate light response is required to be able to explore ways of increasing the open circuit voltage of MABiI₃solar cells. This study shares ideas of why MABiI₃responds inversely to different wavelengths of light.

References:

[1] Park BW, Philippe B, Zhang X, Rensmo H, Boschloo G, Johansson EMJ. Bismuth Based Hybrid Perovskites A3Bi2I9 (A: Methylammonium or Cesium) for Solar Cell Application. Adv Mater. 2015;27(43):6806–13.

[2] Shin J, Kim M, Jung S, Kim CS, Park J, Song A, et al. Enhanced efficiency in lead-free bismuth iodide with post treatment based on a hole-conductor-free perovskite solar cell. Nano Res. 2018;11(12):6283–93.

[3] Singh T, Kulkarni A, Ikegami M, Miyasaka T. Effect of Electron Transporting Layer on Bismuth-Based Lead-Free Perovskite (CH3NH3)3 Bi2I9 for Photovoltaic Applications. ACS Appl Mater Interfaces. 2016;8(23):14542–7.

[4] Hoye RLZ, Lee LC, Kurchin RC, Huq TN, Zhang KHL, Sponseller M, et al. Strongly Enhanced Photovoltaic Performance and Defect Physics of Air-Stable Bismuth Oxyiodide (BiOI). Adv Mater. 2017;29(36).

[5] Ahn N, Son DY, Jang IH, Kang SM, Choi M, Park NG. Highly Reproducible Perovskite Solar Cells with Average Efficiency of 18.3% and Best Efficiency of 19.7% Fabricated via Lewis Base Adduct of Lead(II) Iodide. J Am Chem Soc. 2015;137(27):8696–9.

[6] Yin M, Xie F, Chen H, Yang X, Ye F, Bi E, et al. Annealing-free perovskite films by instant crystallization for efficient solar cells. J Mater Chem A [Internet]. 2016 Dec 7;4(22):8548–53. Available from: http://xlink.rsc.org/?DOI=C6TA02490D

[7] Zhang X, Ye J, Zhu L, Zheng H, Liu G, Liu X, et al. High-efficiency perovskite solar cells prepared by using a sandwich structure MAI-PbI2-MAI precursor film. Nanoscale. 2017;9(14):4691–9.

[8] Jain SM, Phuyal D, Davies ML, Li M, Philippe B, De Castro C, et al. An effective approach of vapour assisted morphological tailoring for reducing metal defect sites in lead-free, (CH3NH3)3Bi2I9bismuth-based perovskite solar cells for improved performance and long-term stability. Nano Energy [Internet]. 2018;49:614–24. Available from: https://doi.org/10.1016/j.nanoen.2018.05.003

Acknowledgements:

Author Z. Parekh is thankful to Materials and Manufactruing Academy (M2A) and KP Technology for funding. In addition, thank you to KP Technology for the experimental support provided and use of their facility. Authors are grateful to European Union's Horizon 2020 research and innovation program.

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