Influence of Grain Size on Ionic Defects in Perovskite Solar Cells
Sandhya Tammireddy a, Carsten Deibel a, Qingzhi An a, Yana Vaynzof a
a Chemnitz University of Technology, Institute of Physics, Reichenhainer Straße, 70, Chemnitz, Germany
b Institute of Applied Physics, TU Dresden, Nöthnitzer Straße, 61, Dresden, Germany
Proceedings of International Conference on Impedance Spectroscopy and Related Techniques in Metal Halide Perovskites (PERIMPED)
Online, Spain, 2020 October 6th - 7th
Organizers: Juan Bisquert, Bruno Ehrler and Eline Hutter
Poster, Sandhya Tammireddy, 027
Publication date: 25th September 2020

Metal halide perovskites, such as methylammonium lead triiodide (MAPbI3), achieved  attention of the PV community during last few years. Despite the rapid progress, the device performance of perovskite solar cells still remains below their theoretical limit. One of the key factors to further improve their power conversion efficiency is to develop high-quality perovskite active layers with large grain size, and hence reduced defect density. In our contribution, through impedance spectroscopy and deep-level transient spectroscopy, we characterize ionic defects in MAPbI3-based devices in which the grain size was purposely varied: by adding hypophosphorous acid (HPA) in the precursor solution, the average grain size increases . Our results indicate that the activation energy and concentration of an ionic defect species which we assign to methylammonium vacancies decrease with the amount of HPA. Therefore, controlled grain growth during fabrication facilitates an opportunity in tuning the ionic defects in perovskite devices.

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