This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record . Please cite this article as doi: 10.1002/ente.201900343 This article is protected by copyright. All rights reserved DOI: 10.1002/ente.201900343 Article type: Full Paper Evolution of Perovskite Crystallization in Printed Mesoscopic Perovskite Solar Cells Oliver Filonik, Margret E. Thordardottir, Jenny Lebert, Stephan Pröller, Sebastian Weiß, Lew J. Haur, Anish Priyadarshi, Philippe Fontaine, Peter Müller-Buschbaum, Nripan Mathews and Eva M. Herzig* ((Optional Dedication)) Oliver Filonik, Margret E. Thordardottir, Dr. Jenny Lebert, Dr. Stephan Pröller, Sebastian Weiß, Prof. Eva M. Herzig Technische Universität München, Munich School of Engineering, Herzig Group, Lichtenbergstr. 4a, 85748 Garching, Germany E-mail: Eva.Herzig@uni-bayreuth.de Margret E. Thordardottir, Prof. Peter Müller-Buschbaum Technische Universität München, Physik-Department, Lehrstuhl für Funktionelle Materialien, James-Franck-Str. 1, 85748 Garching, Germany Lew J. Haur, Dr. Anish Priyadarshi, Prof. Nripan Mathews Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, Singapore, 637553 Singapore Prof. Nripan Mathews School of Materials Science and Engineering, Nanyang Technological University, Singapore, 639798 Singapore Dr. Philippe Fontaine Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-Yvette Cedex, France Prof. Peter Müller-Buschbaum Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1, D-85748 Garching, Germany Prof. Eva M. Herzig Universität Bayreuth, Physikalisches Institut, Dynamik und Strukturbildung - Herzig Group, Universitätsstr. 30, 95447 Bayreuth, Germany Keywords: in-situ GIWAXS, crystallization, mesoscopic, perovskite solar cell Accepted Article aur, Anish , Anish Pri and Eva M. H d Eva M l Dedication) l Dedicatio onik, Margre ik, Marg of. Eva M. He of. Eva M. he Universität Universi ergstr. 4a, 857 rgstr. 4a, 8 va.Herzig@u .Herzig@ E. Thordardot E. Thord he Universität he Univer anck- Str. r. 1, 8 1 aur, Dr. Anish aur, Dr. An esearch Instit earch Ins ingapore apore pan Mathews Mathew Materials Sc Materials ingapore ngapore pe Fontaine Fontaine on SOLEIL, SOLEI ance ce r Müller Müller- -Bus B ier r- -Leibnitz Z Leibnit Garching, Ge rching, M. Herzig Herzig A ät Bayreuth, P t Bayreuth ätsstr. ätsstr 30, 954 3