PHOTOCONDUCTIVITY DYNAMICS IN LEAD HALIDE PEROVSKITES PROBED BY SCANNING PROBE MICROSCOPY
Tirmzi, Syed Ali Moeed
Lead halide perovskite is an emerging class of solar material that make high efficiency solar cells. Despite the impressive efficiency records, lead-halide perovskite devices suffer from reversible and irreversible changes under illumination Understanding photo-induced changes requires understanding charge dynamics and defect chemistry. We use scanning probe microscopy techniques including time resolved EFM (tr-EFM), phase-kick EFM (pk-EFM), broadband local dielectric spectroscopy (BLDS), and dissipation microscopy to probe samples response to light irradiation in number of different lead halide perovskite. Our new approach to the description of electrical scanning probe measurement has led to a powerful new interpretation of these measurements in terms of the sample impedance. We present direct evidence that the slow and fast charge dynamics ubiquitously seen in 3D lead-halide perovskites have a common origin related to a highly activated charge redistribution. Our data shows that perovskite conductivity can be highly substrate dependent due to defect chemistry presumably in the grown perovskite dictated by the growth substrate. We find absence of slow dynamics in the 2D perovskite samples. These observations and results emphasize the need to include photoionic conductivity and defect generation in perovskite solar cell device modeling.
electric force microscopy; impedance microscopy; kelvin probe force microscopy; lead halide perovskite; scanning probe microscopy; solar cells
Wise, Frank; Hanrath, Tobias
Chemistry and Chemical Biology
Ph. D., Chemistry and Chemical Biology
Doctor of Philosophy
dissertation or thesis
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