Regensburg 2019 – wissenschaftliches Programm
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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.