Polypyridyl Iron Complex as a Hole-Transporting Material for Formamidinium Lead Bromide Perovskite Solar Cells
journal contributionposted on 14.07.2017 by Muhammad K. Kashif, Iacopo Benesperi, Rebecca A. Milhuisen, Steffen Meyer, Jack Hellerstedt, David Zee, Noel W. Duffy, Barry Halstead, Michael S. Fuhrer, John Cashion, Yi-Bing Cheng, Leone Spiccia, Alexandr N. Simonov, Udo Bach
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An efficient hole-transporting material (HTM) is indispensable for high-performing perovskite solar cells (PSCs), which have recently emerged as a breakthrough photovoltaic technology. Here, we demonstrate the capacity of the transition metal complex (6,6′-bis(1,1-di(pyridin-2-yl)ethyl)-2,2′-bipyridine)-iron(II/III) trifluoromethanesulfonate ([Fe(bpyPY4)](OTf)2+x) to act as an additive-free, solution-processable HTM in PSCs based on the formamidinium lead bromide absorber. State-of-the-art physical methods have been employed to characterize [Fe(bpyPY4)](OTf)2+x and, in particular, to demonstrate its significantly higher conductivity compared to that of the conventional HTM spiro-OMeTAD. A maximum power conversion efficiency of 2.2% was obtained for a device employing [Fe(bpyPY4)](OTf)2+x, which is the first evidence of the applicability as a HTM in a PSC of a solid material in which conductivity is provided by a redox transformation of a transition metal.