The Role of SnF<sub>2</sub> Additive on Interface Formation in All Lead‐Free FASnI<sub>3</sub> Perovskite Solar Cells
Julia Zillner, H.‐G. Boyen, Philip Schulz, Jonas Hanisch, Nicolas Gauquelin, Johan Verbeeck, Johannes Küffner, Derese Desta, Lisa Eisele, Erik Ahlswede, Michael Powalla
Abstract
Abstract Tin‐based perovskites are promising alternative absorber materials for lead‐free perovskite solar cells but need strategies to avoid fast tin (Sn) oxidation. Generally, this reaction can be slowed down by the addition of tin fluoride (SnF 2 ) to the perovskite precursor solution, which also improves the perovskite layer morphology. Here, this work analyzes the spatial distribution of the additive within formamidinium tin triiodide (FASnI 3 ) films deposited on top of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transporting layers. Employing time‐of‐flight secondary ion mass spectrometry and a combination of hard and soft X‐ray photoelectron spectroscopy, it is found that SnF 2 preferably accumulates at the PEDOT:PSS/perovskite interface, accompanied by the formation of an ultrathin SnS interlayer with an effective thickness of ≈1.2 nm.