Explanation for Reduced IV-Curve Hysteresis in Highly Efficient Perovskite Solar Cells
Stephane Altazin a, Beat Ruhstaller a b, Martin Neukom a b, Evelyne Knapp b
a ICP, ZHAW, Wildbachstr. 21, Winterthur, 8401, Switzerland
Proceedings of Perovskite Thin Film Photovoltaics (ABXPV17)
València, Spain, 2017 March 1st - 2nd
Organizers: Henk Bolink and David Cahen
Oral, Martin Neukom, presentation 077
Publication date: 18th December 2016

There is increasing evidence that the presence of mobile ions in perovskite solar cells can cause a current-voltage curve hysteresis. It is however still under debate how exactly mobile ions influence the device operation [1, 2]. We use drift-diffusion simulations incorporating mobile ions to describe IV-curves of preconditioned methylammonium lead iodide perovskite solar cells and compare them with experimental results. The occurrence of hysteresis is also related to the contact layer materials [3]. Hereby the following question arises: If mobile ions in the bulk are responsible for the IV-curve hysteresis, why does the hysteresis depend on the contact materials? And why do highly efficient devices generally show low hysteresis?
Our simulation results show that the hysteresis depends on the extent of surface recombination and on the diffusion-length of charge carriers. We provide a detailed explanation for the reduced hysteresis of perovskite solar cells with high power conversion efficiencies. We find that in high-efficiency solar cells ion migration is still present, but does not cause a hysteresis effect. This finding is consistent with findings from Calado et al. that showed the presence of mobile ions in devices without IV-curve hysteresis [4]. In such devices charge extraction is mainly driven by diffusion of free electrons and holes.

[1] W. Tress, N. Marinova, T. Moehl, S. M. Zakeeruddin, M. K. Nazeeruddin, M. Grätzel, Energy Environ. Sci., 2015, 8, 995.
[2] D. W. deQuilettes, W. Zhang, V. M. Burlakov, D. J. Graham, T. Leijtens, A. Osherov, V. Bulovic, H. J. Snaith, D. S. Ginger, S. D. Stranks, Nature Comm., 2016, 7, 11683.
[3] W. Nie, H. Tsai, R. Asadpour, J.-C. Blancon, A. J. Neukirch, G. Gupta, J. J. Crochet, M. Chhowalla, S. Tretiak, M. A. Alam, H.-L. Wang, A. D. Mohite, Science, 2015, 347, 522-525.
[4] P. Calado, A. M. Telford, D. Bryant, X. Li, J. Nelson, B. C. O’Regan, P. R. F. Barnes, arXiv:1606.00818.

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