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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 61: Focus: Fundamental Physics of Perovskites II - organized by Lukas Schmidt-Mende and Vladimir Dyakonov
CPP 61.6: Topical Talk
Donnerstag, 15. März 2018, 11:15–11:45, C 130
Understanding Hysteresis in Perovskite Solar Cells — •Stefan A.L. Weber1,2, Ilka M. Hermes1, Niklas M. Budinger1,2, Wolfgang Tress3, Anders Hagfeldt3, Michael Graetzel3, and Rüdiger Berger1 — 1MPI for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany — 2Johannes Gutenberg University, Department of Physics, Staudingerweg 10, 55128 Mainz, Germany. — 3Laboratory of Photomolecular Science, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
We explain the underlying mechanism of hysteresis in a hybrid lead-halide perovskite solar cell by measuring and numerically calculating the dynamics of the charge distribution in an operating device. The origin, magnitude and the dynamics of the charge re-distribution processes that are responsible for hysteresis in the device are still not understood. We developed a method based on Kelvin probe force microscopy that enables mapping charge re-distribution in an operating device upon a voltage- or light pulse with sub-millisecond resolution. A combination of an asymmetric ion migration and the formation of a surface dipole at the anode shielded the electric field in the perovskite layer within 10 ms after applying a forward voltage to the device. After switching off the voltage, the anode surface dipole created a reverse electric field in the cell that lasted for up to 500 ms. This reverse electric field increases charge carrier extraction and thereby directly explains higher photocurrents during reverse bias scans.