Regensburg 2016 – scientific programme

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DS: Fachverband Dünne Schichten

DS 11: Hybrid and Perovskite Photovoltaics I
(Joint session of CPP, DS and HL, organized by CPP)

DS 11.7: Talk

Monday, March 7, 2016, 16:45–17:00, H38

Iodine Migration and its Effect on Hysteresis in Perovskite Solar Cells — Cheng Li¹, Steffen Tscheuscher², Fabian Paulus³, Paul Hopkinson³, Johannes Kiessling¹, Anna Köhler², Yana Vaynzof³, and •Sven Hüttner¹ — ¹Organic and Hybrid Electronics, Makromol. Chemie I, Universität Bayreuth — ²Experimentalphysik II, Universität Bayreuth — ³Centre for Advanced Materials, Universität Heidelberg

Solution-processed organic-inorganic hybrid perovskite solar cells (e.g. CH₃NH₃PbI₃−xCl_x) currently exhibit promising performances. However, the origin of the observed hysteresis in the current-voltage (J-V) curves, i.e. the sweeping-history-dependent electrical current, is still not sufficiently understood. To investigate its origin we employ electroabsorption (EA) spectroscopy to explore the built-in potential in working photovoltaic devices. Furthermore, we study the temperature dependent dynamic processes in perovskite solar cells by characterizing their current-voltage behavior at different temperatures. The electrical current relaxation process during temperature dependent J-V measurements provides the evidence of the migration of ions. In order to investigate the nature of these ions, we further present X-ray photoemission spectroscopy (XPS) experiments which shows the elemental redistribution after applying an electrical bias. The results give a concise picture that mainly iodide ions can be driven by an external electrical field and then accumulate at the respective perovskite/electrode interfaces. The migration and accumulation of iodide ions create a modulation of the respective interfacial barriers which is the origin of the hysteresis.