Volume 13 No. 31 August 18 2017 Vol. 29 No. 31 August 18 2017 www.advmat.de Solar Technologies go Hybrid Scientists of five Bavarian universities joined together in the state funded research network Solar Technologies go Hybrid (SolTech) to synergize their research and explore the full use of sunlight as the principal energy source of our planet. The SolTech network covers all fields of research on solar energy use, i.e., the conversion of solar energy to electricity for immediate use and the conversion of solar energy into chemical energy for storage and future use. Cover image by Christoph Hohmann, Nanosystems Initiative Munich (NIM). Advanced Materials has been bringing you the best in materials research for over twenty years. With its increased ISI Impact Factor of 19.791, Advanced Materials is one of the most influential journals in the field. Publishing every week, Advanced Materials now brings you even more of the latest results at the cutting edge of materials science. www.advmat.de In article number 1700264, Sven Hüttner, Pablo Docampo, and co-workers give an overview of hybrid metal halide perovskites for solar cell applications. The focus is on the series of challenges that have been overcome and those still remaining to be solved. In particular, the authors lay out their understanding of the perovskite crystallization process and how this knowledge can be harnessed to enable better performing devices; how to overcome reproducibility and hysteresis issues; and the long-term prospects of the technology in terms of stability and sustainability. Image by Criss Hohmann (Nanosystems Initiative Munich). www.small-journal.com 31/2017 Hybrid Photovoltaics In hybrid photovoltaics an organic and an inorganic semiconductor are combined in the active layer to have the advantages of both material classes in a single device. In article number 1700248, Peter Müller-Buschbaum and co-workers review research related to hybrid solar cells which combine conjugated polymers with inorganic materials such as titanium dioxide, zinc oxide, silicon, germanium and quantum dots. Hybrid solar cells based on crystalline Si are discussed for comparison. Particular emphasis is put on different routes to tailor nanostructures of the organic or inorganic component. Cover Image by Christoph Hohmann, Nanosystems Initiative Munich (NIM). Soft but Powerful Artificial Muscles Based on 3D Graphene CNT Ni Heteronanostructures I.-K. Oh and co-workers Small is the very best interdisciplinary forum for all experimental and theoretical aspects of fundamental and applied research at the micro and nano length scales. With an ISI impact Factor of 8.643 and publishing every week with papers online in advance of print, Small is your first-choice venue for topquality communications, detailed full papers, cutting-edge concepts, and in-depth reviews of all things micro and nano. www.small-journal.com Adv. Energy Mater. 2017, 7, 1770086 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com (1 of 5) 1770086
Contents EDITORIAL P. Müller-Buschbaum...1701977 Solar Technologies go Hybrid ReviewS M. L. Petrus, J. Schlipf, C. Li, T. P. Gujar, N. Giesbrecht, P. Müller-Buschbaum, M. Thelakkat, T. Bein, S. Hüttner,* P. Docampo*...1700264 Capturing the Sun: A Review of the Challenges and Perspectives of This review of perovskite solar cells discusses the current understanding of the perovskite crystallization process, and how this knowledge can be harnessed to enable better performing devices; how to overcome reproducibility issues and mitigate hysteresis; and the long-term prospects of perovskite solar cell technology in terms of stability, cost, and sustainability. Hybrid Photovoltaics P. Müller-Buschbaum,* M. Thelakkat, T. F. Fässler, M. Stutzmann...1700248 Hybrid Photovoltaics from Fundamentals towards Application In hybrid photovoltaics, an organic and an inorganic semiconductor are combined in the active layer to realize the conversion of light into charge carriers which can be harvested. This review highlights hybrid solar cells which combine conjugated polymers with inorganic materials such as titanium dioxide, zinc oxide, silicon, germanium and quantum dots. Conjugated Polymers R. Hildner, A. Köhler, P. Müller-Buschbaum, F. Panzer, M. Thelakkat*...1700314 π-conjugated Donor Polymers: Structure Formation and Morphology in Solution, Bulk and Photovoltaic Blends A systematic correlation of structure formation of donor-type π-conjugated polymers in solution using optical spectroscopy and in bulk or thin films as well as in photovoltaic blends using scattering techniques (SAXS, WAXS, GIWAXS) is given. The main focus is on the correlation of structures, morphology and mole cular chain orientation as a function of molecular weight, dispersity, intramolecular and intermolecular interactions and innovative processing techniques. 1770086 (2 of 5) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Adv. Energy Mater. 2017, 7, 1770086
The photophysical properties of the electronically excited states of mole cular aggregates are dictated by the mutual interactions of their building blocks and lead commonly to the formation of delocalized exciton states. After summarizing the theoretical background a survey of experiments on various material systems ranging from natural photosynthetic assemblies to self assembled artificial dye arrangements is provided. Review Molecular Aggregates T. Brixner, R. Hildner, J. Köhler,* C. Lambert, F. Würthner...1700236 Exciton Transport in Molecular Aggregates From Natural Antennas to Synthetic Chromophore Systems Contents Metal halide perovskites have emerged as a promising new class of material for light-emitting and photovoltaic applications owing to their outstanding optical and optoelectronic properties. This research news provides an overview of the current state-of-the-art of quantum-confinement effects in perovskite nanocrystals, with a focus on synthetic strategies and resulting optical properties, characterization methods, and emerging applications. Optoelectronics L. Polavarapu,* B. Nickel, J. Feldmann, A. S. Urban*...1700267 Advances in Quantum-Confined Perovskite Nanocrystals for Optoelectronics Three promising applications of crosslinking in organic solar cells are reviewed. Most importantly, crosslinking is used to stabilize the blend morphology in bulk heterojunction solar cells. In addition, stable interlayers can be formed and crosslinking enables solution processing of multilayer devices. A third possibility is the stabilization of nanoimprinted patterns in the active layers. Organic Solar Cells F.-J. Kahle, C. Saller, A. Köhler, P. Strohriegl*...1700306 Crosslinked Semiconductor Polymers for Photovoltaic Applications Charge-transfer states play an important role in organic solar cells, and generally in many new materials that are aimed at converting sunlight into other forms of energy. The incorrect description of charge-transfer excitations is considered one of the hallmark failures of timedependent density functional theory. The problem has been overcome by the development of nonempirically tuned range-separated hybrid functionals. Charge Transfer S. Kümmel...1700440 Charge-Transfer Excitations: A Challenge for Time-Dependent Density Functional Theory That Has Been Met Adv. Energy Mater. 2017, 7, 1770086 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim (3 of 5) 1770086
Contents Water Oxidation Catalysts V. Kunz, D. Schmidt, M. I. S. Röhr, R. Mitrić,* F. Würthner*...1602939 Supramolecular Approaches to Improve the Performance of Ruthenium-Based Water Oxidation Catalysts Supramolecular principles can be utilized to enhance the activity of homogeneous ruthenium water oxidation catalysts. Focusing on two different water oxidation mechanisms, recent examples from literature are described where noncovalent forces are exploited to accelerate the rate of water oxidation. Those interactions facilitate the interplay of catalytic centers with substrate water molecules or other catalytic subunits to lower activation barriers. Covalent Organic Frameworks D. D. Medina,* T. Sick, T. Bein*...1700387 Photoactive and Conducting Covalent Organic Frameworks Hierarchical functional materials with properties encoded for a defined functionality such as light-induced charge separation are highly desirable targets of numerous synthetic efforts. In this research news article, an overview is provided on newly emerging photoactive and conducting 2D covalent organic frameworks, sketching the creative trajectory from subunit design strategies to framework construction and resulting functionalities. Organic Solar Cells T. Linderl, T. Zechel, M. Brendel, D. Moseguí González, P. Müller-Buschbaum, J. Pflaum, W. Brütting*...1700237 Energy Losses in Small-Molecule Organic Photovoltaics The energy loss between the optical gap and the open-circuit-voltage is one of the primary reasons why the efficiency of organic photovoltaic cells lags behind their inorganic counterparts. This research news highlights the scientific background and presents strategies to improve on this issue. How to contact us: Editorial Office: Phone: (+49) 6201-606-235/432 Fax: (+49) 6201-606-500 Email: advenergymat@wiley-vch.de Reprints: cherth@wiley-vch.de Copyright Permission: Fax: (+49) 6201-606-332 Email: rights@wiley-vch.de 1770086 (4 of 5) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Adv. Energy Mater. 2017, 7, 1770086
The latest results on structural dynamics and their impact on selected optical properties in methylammonium lead iodide perovskites are highlighted. Temperature-dependent optical spectroscopy gives access to their electronic nature and enables strong correlations to respective structural properties. Ion migration and the presence of induced ions strongly affect the slow dynamics of optical properties, which are reviewed in particular herein. Perovskites F. Panzer, C. Li, T. Meier, A. Köhler, S. Huettner*...1700286 Impact of Structural Dynamics on the Optical Properties of Methylammonium Lead Iodide Perovskites Contents Grazing-incidence X-ray scattering is a powerful tool for investigating the morphology of hybrid perovskite thin films. This research news covers a broad range of grazing-incidence small- and wide-angle X-ray scattering studies and sheds light on the remarkable possibilities these methods offer for understanding film morphology, film formation, crystallization, and degradation mechanisms when combined with advanced data treatment. Solar Cells J. Schlipf, P. Müller-Buschbaum*...1700131 Structure of Organometal Halide Perovskite Films as Determined with Grazing-Incidence X-Ray Scattering Methods Hybrid photoconductive cathode interlayers based on zinc oxide doped with perylene bisimide dye molecules show increased conductivity under light irradiation due to enhanced electron mobility and carrier density, enabling high performance polymer solar cells at interlayer thickness of up to 100 nm, which is desired for roll-to-roll processing techniques to facilitate mass production of photovoltaic modules. Polymer Solar Cells Z. Xie,* F. Würthner*...1602573 Hybrid Photoconductive Cathode Interlayer Materials Composed of Perylene Bisimide Photosensitizers and Zinc Oxide for High Performance Polymer Solar Cells Adv. Energy Mater. 2017, 7, 1770086 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim (5 of 5) 1770086