TY - JOUR A1 - Cappel, Ute B. A1 - Svanstrom, Sebastian A1 - Lanzilotto, Valeria A1 - Johansson, Fredrik O. L. A1 - Aitola, Kerttu A1 - Philippe, Bertrand A1 - Giangrisostomi, Erika A1 - Ovsyannikov, Ruslan A1 - Leitner, Torsten A1 - Föhlisch, Alexander A1 - Svensson, Svante A1 - Martensson, Nils A1 - Boschloo, Gerrit A1 - Lindblad, Andreas A1 - Rensmo, Hakan T1 - Partially Reversible Photoinduced Chemical Changes in a Mixed-Ion Perovskite Material for Solar Cells JF - ACS applied materials & interfaces N2 - Metal halide perovskites have emerged as materials of high interest for solar energy-to-electricity conversion, and in particular, the use of mixed-ion structures has led to high power conversion efficiencies and improved stability. For this reason, it is important to develop means to obtain atomic level understanding of the photoinduced behavior of these materials including processes such as photoinduced phase separation and ion migration. In this paper, we implement a new methodology combining visible laser illumination of a mixed-ion perovskite ((FAP-bI(3))(0.85)(MAPbBr(3))(0.15)) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites. KW - photoelectron spectroscopy KW - laser illumination KW - lead halide perovskite KW - ion migration KW - phase separation KW - stability Y1 - 2017 U6 - https://doi.org/10.1021/acsami.7b10643 SN - 1944-8244 VL - 9 SP - 34970 EP - 34978 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Zehbe, Kerstin A1 - Kollosche, Matthias A1 - Lardong, Sebastian A1 - Kelling, Alexandra A1 - Schilde, Uwe A1 - Taubert, Andreas T1 - Ionogels Based on Poly(methyl methacrylate) and Metal-Containing Ionic Liquids: Correlation between Structure and Mechanical and Electrical Properties JF - International journal of molecular sciences N2 - Ionogels (IGs) based on poly(methyl methacrylate) (PMMA) and the metal-containing ionic liquids (ILs) bis-1-butyl-3-methlimidazolium tetrachloridocuprate(II), tetrachloride cobaltate(II), and tetrachlorido manganate(II) have been synthesized and their mechanical and electrical properties have been correlated with their microstructure. Unlike many previous examples, the current IGs show a decreasing stability in stress-strain experiments on increasing IL fractions. The conductivities of the current IGs are lower than those observed in similar examples in the literature. Both effects are caused by a two-phase structure with micrometer-sized IL-rich domains homogeneously dispersed an IL-deficient continuous PMMA phase. This study demonstrates that the IL-polymer miscibility and the morphology of the IGs are key parameters to control the (macroscopic) properties of IGs. KW - microstructure KW - ionogels KW - ionic liquids KW - phase separation KW - mechanical properties KW - ionic conductivity Y1 - 2016 U6 - https://doi.org/10.3390/ijms17030391 SN - 1422-0067 VL - 17 PB - MDPI CY - Basel ER - TY - JOUR A1 - Cardinaletti, Ilaria A1 - Kesters, Jurgen A1 - Bertho, Sabine A1 - Conings, Bert A1 - Piersimoni, Fortunato A1 - Lutsen, Laurence A1 - Nesladek, Milos A1 - Van Mele, Bruno A1 - Van Assche, Guy A1 - Vandewal, Koen A1 - Salleo, Alberto A1 - Vanderzande, Dirk A1 - Maes, Wouter A1 - Manca, Jean V. T1 - Toward bulk heterojunction polymer solar cells with thermally stable active layer morphology JF - Journal of photonics for energy N2 - When state-of-the-art bulk heterojunction organic solar cells with ideal morphology are exposed to prolonged storage or operation at elevated temperatures, a thermally induced disruption of the active layer blend can occur, in the form of a separation of donor and acceptor domains, leading to diminished photovoltaic performance. Toward the long-term use of organic solar cells in real-life conditions, an important challenge is, therefore, the development of devices with a thermally stable active layer morphology. Several routes are being explored, ranging from the use of high glass transition temperature, cross-linkable and/or side-chain functionalized donor and acceptor materials, to light-induced dimerization of the fullerene acceptor. A better fundamental understanding of the nature and underlying mechanisms of the phase separation and stabilization effects has been obtained through a variety of analytical, thermal analysis, and electro-optical techniques. Accelerated aging systems have been used to study the degradation kinetics of bulk heterojunction solar cells in situ at various temperatures to obtain aging models predicting solar cell lifetime. The following contribution gives an overview of the current insights regarding the intrinsic thermally induced aging effects and the proposed solutions, illustrated by examples of our own research groups. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. KW - organic photovoltaics KW - bulk heterojunction KW - thermal stability KW - phase separation KW - lifetime Y1 - 2014 U6 - https://doi.org/10.1117/1.JPE.4.040997 SN - 1947-7988 VL - 4 PB - SPIE CY - Bellingham ER -