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DS: Fachverband Dünne Schichten

DS 14: Poster

DS 14.1: Poster

Dienstag, 2. April 2019, 17:00–20:00, Poster E

Grain Boundaries Act as Solid Walls for Charge Carrier Diffusion in Large Crystal MAPI Thin Films — •Frank Schäfer¹, Richard Ciesielski¹, Nicolai Hartmann¹, Nadja Giesbrecht¹, Thomas Bein¹, Pablo Docampo², and Achim Hartschuh¹ — ¹Department Chemie und Center for Nanoscience (CeNS), LMU München, Deutschland — ²School of Electrical and Electronic Engineering, Newcastle University, United Kingdom

Micro- and nanocrystalline methylammonium lead iodide (MAPI)-based thin-film solar cells today reach power conversion efficiencies of over 20%. We investigate the impact of grain boundaries on charge carrier transport in large crystal MAPI thin films using time-resolved photoluminescence (PL) microscopy and numerical model calculations. Crystal sizes in the range of several tens of micrometers allow for the spatially and time resolved study of boundary effects. Whereas long-ranged diffusive charge carrier transport is observed within single crystals, no detectable diffusive transport occurs across grain boundaries. The observed PL transients are found to crucially depend on the microscopic geometry of the crystal and the point of observation. In particular, spatially restricted diffusion of charge carriers leads to slower PL decay near crystal edges as compared to the crystal center. In contrast to many reports in the literature, our experimental results show no quenching or additional loss channels due to grain boundaries for the studied material, which thus do not negatively affect the performance of the derived thin-film devices.