Charge Extraction Imaging by Potentiostatic Photoluminescence Microscopy
Lukas Wagner a b c, Patrick Schygulla b c, Jan Philipp Herterich b d, Mohamed Elshamy b, Dmitry Bogachuk b c, Salma Zouhair b e, Simone Mastroianni b d, Uli Würfel b d, Yuhang Liu f, Shaik M. Zakeeruddin f, Michael Grätzel f, Jan Christoph Goldschmidt a, Andreas Hinsch b, Stefan W. Glunz b c
a Solar Energy Conversion Group, Department of Physics, University Marburg, Germany.
b Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, 79110 Freiburg, Germany.
c Laboratory for Photovoltaic Energy Conversion, University of Freiburg, Emmy-Noether-Straße 2, 79110 Freiburg, Germany.
d Freiburg Materials Research Center FMF, University of Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg, Germany.
e Abdelmalek Essaadi University, FSTT, Thin Films & Nanomaterials Lab, 90000 Tangier, Morocco.
f Laboratory of Photonics and Interfaces (LPI), École Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland.
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV23)
London, United Kingdom, 2023 June 12th - 14th
Organizers: Tracey Clarke, James Durrant and Trystan Watson
Poster, Lukas Wagner, 278
Publication date: 30th March 2023

We introduce a method for microscopically resolved imaging of the photocurrent and the charge extraction efficiency. As derived from basic physical considerations and demonstrated on near-to-ideal III-V solar cells, we demonstrate that electrical-bias-dependent photoluminescence (PL) images reveal fundamental information on charge extraction of photovoltaic devices. This characterization is especially relevant to liquid-processed optoelectrical devices such es perovskite solar cells, where inhomogeneities in layer deposition are a key factor that limits device performance. For such perovskite devices, we show how voltage-dependent photoluminescence (PL(V)) images can be translated into maps of local current-density voltage (J(V)) curves. Furthermore, we demonstrate how the assessment can be used to identify four characteristic morphological defects, such as degraded perovskite or interrupted coating of contact layers, that reduce local charge extraction or induce non-radiative recombination. As this method can be implemented with only a photoluminescence microscope and a source meter, it can be a powerful research tool for a deeper understanding of the working properties of perovskite solar cells as well as for the performance optimization linked to layer deposition and interface formation.

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