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Enhanced stability and efficiency in hole-transport-layer-free CsSnI3 perovskite photovoltaics

Nature Energy volume 1, Article number: 16178 (2016) Cite this article

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Abstract

Photovoltaics based on tin halide perovskites have not yet benefited from the same intensive research effort that has propelled lead perovskite photovoltaics to >20% power conversion efficiency, due to the susceptibility of tin perovskites to oxidation, the low energy of defect formation and the difficultly in forming pinhole-free films. Here we report CsSnI3 perovskite photovoltaic devices without a hole-selective interfacial layer that exhibit a stability ∼10 times greater than devices with the same architecture using methylammonium lead iodide perovskite, and the highest efficiency to date for a CsSnI3 photovoltaic: 3.56%. The latter largely results from a high device fill factor, achieved using a strategy that removes the need for an electron-blocking layer or an additional processing step to minimize the pinhole density in the perovskite film, based on co-depositing the perovskite precursors with SnCl2. These two findings raise the prospect that this class of lead-free perovskite photovoltaic may yet prove viable for applications.

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Figure 1: Evolution of the absorption spectrum of CsSnI3 films with different tin halide additives in ambient air.
Figure 2: SEM images of CsSnI3 films on ITO glass prepared with different tin halide additives.
Figure 3: Evolution of XRD patterns of CsSnI3 films with and without SnCl2 additive under different conditions.
Figure 4: HRXPS Cl 2p spectra of films of SnCl2 and CsSnI3 + 10 mol% SnCl2 before and after exposure to ambient air.
Figure 5: Current–voltage (JV) characteristics of CsSnI3 PPVs before and after a period of extended storage under nitrogen.
Figure 6: Band diagrams depicting the energy level alignment at the ITO/PC61BM interface and spectroscopic evidence for an n-type doping interaction.
Figure 7: PPV device stability tests under 1 sun constant illumination in ambient air for unencapsulated devices with the same architecture.

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Acknowledgements

The authors would like to thank the United Kingdom Engineering and Physical Sciences Research Council (EPSRC) for funding (Grant numbers: EP/L505110/1 & EP/N009096/1). All data supporting this study are provided as Supplementary Information accompanying this paper.

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Authors and Affiliations

  1. Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK

    K. P. Marshall, R. I. Walton & R. A. Hatton

  2. Department of Physics, University of Warwick, Coventry CV4 7AL, UK

    M. Walker

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Contributions

K.P.M. performed all of the experimental work. K.P.M., R.I.W. and R.A.H. conceived the experiments, analysed the results and wrote the paper. M.W. collected the XPS and UPS data and helped to analyse the results.

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Correspondence to R. A. Hatton.

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The authors declare no competing financial interests.

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Supplementary Information

Supplementary Figures 1–14, Supplementary Tables 1–6, Supplementary Discussion. (PDF 1927 kb)

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Marshall, K., Walker, M., Walton, R. et al. Enhanced stability and efficiency in hole-transport-layer-free CsSnI3 perovskite photovoltaics. Nat Energy 1, 16178 (2016). https://doi.org/10.1038/nenergy.2016.178

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